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# Lakhmir Singh solutions Physics for Class 10 (2019 Exam) chapter 5 Refraction of Light

## Chapter 5 - Refraction of Light

#### Pages 171 - 470

If a ray of light goes from a rarer medium to a denser medium, will it bend towards the normal or away from it?

Q 1 | Page 219

What happens when a ray of light falls normally (or perpendiculary) on the surface of a plane mirror?

Q 1 | Page 173

A beam of light travelling in a rectangular glass slab emerges into air. Draw a ray-diagram indicating the change in its path.

Q 1 | Page 219

What kind of lens is present in the human eye?

Q 1 | Page 269

A ray of light is incident on a plane mirror at an angle of 30°. What is the angle of reflection

Q 2 | Page 173

Name two parts of the eye which refract light rays (or bend light rays).

Q 2 | Page 269

If a ray of light goes form a denser medium to a rarer medium, will it bend towards the normal or away from the normal?

Q 2 | Page 219

A ray of light strikes a plane mirror at an angle of 40° to the mirror surface. What will be the angle of reflection?

Q 3 | Page 173

Name the part of the eye:

which controls the amount of light entering the eye.

Q 3.1 | Page 269

Name the part of the eye:

on which the image is formed.

Q 3.2 | Page 269

Name the part of the eye:

which changes the focal length of eye-lens.

Q 3.3 | Page 269

A beam of light travelling in air is incident of water. Draw a ray-diagram indicating the change in its path in water.

Q 4 | Page 219

What is the name of:

the curved, transparent front surface of the eye?

Q 4.1 | Page 269

A ray of light is incident normally on a plane mirror. What will be the

angle of incidence?

Q 4.1 | Page 173

A ray of light is incident normally on a plane mirror. What will be the

angle of reflection?

Q 4.2 | Page 173

What is the name of:

the light-sensitive layer in the eye?

Q 4.2 | Page 269

Where is the image formed in a human eye?

Q 5 | Page 269

A ray of light travelling in water emerges into air. Draw a ray-diagram indicating the change in its path.

Q 5 | Page 219

What type of image is formed:

in a plane mirror?

Q 5.1 | Page 173

What type of image is formed:

on a cinema screen?

Q 5.2 | Page 173

A ray of light travelling in air is incident on a parallel-sided glass slab (or rectangular glass slab). Draw a ray-diagram indicating the change in its path in glass.

Q 6 | Page 219

What is the function of the lens in the human eye?

Q 6 | Page 269

What kind of mirror is required for obtaining a virtual image of the same size as the object?

Q 6 | Page 173

What is the name of the phenomenon in which the right side of an object appears to be the left side of the image in a plane mirror?

Q 7 | Page 173

A ray of light travelling in glass emerges into air. State whether it will bend towards the normal or away from the normal.

Q 7 | Page 219

What job does the pupil of the eye do?

Q 7 | Page 269

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

Q 8 | Page 219

How does the eye adjust to take account of an increase in brightness?

Q 8 | Page 269

Name the phenomenon responsible for the following effect:
When we sit in front of a plane mirror and write with our right hand, if appears in the mirror that we are writing with the left hand.

Q 8 | Page 173

Name that part of the eye which is equivalent to the photographic film in a camera.

Q 9 | Page 269

If an object is placed at a distance of 10 cm in from of a plane mirror, how far would it be from its image?

Q 9 | Page 173

A ray of light goes from water into air. Will it bend towards the normal or away from the normal?

Q 9 | Page 219

Which property of light makes a pencil cast a shadow when it is held in front of a light source?

Q 10 | Page 173

State two effects caused by the refraction of light.

Q 10 | Page 219

Name the part of the retina which is insensitive to light.

Q 10 | Page 269

Name the phenomenon due to which a swimming pool appears less deep than it really is.

Q 11 | Page 219

The image seen in a plane mirror cannot be formed on a screen. What name is given to this type of image?

Q 11 | Page 173

Fill in the following blank with a suitable word:
When light is reflected, the angles of incidence and reflection are ............ .

Q 12 | Page 173

Name two types of cells in the retina of an eye which respond to light.

Q 12 | Page 269

When a ray of light passes from air into glass, is the angle of refraction greater than or less than the angle of incidence?

Q 12 | Page 219

A ray of light passes from air into a block of glass. Does it bend towards the normal or away from it?

Q 13 | Page 220

State whether the following statement is true of false:
A student says that we can see an object because light from our eyes is reflected back by the object.

Q 13 | Page 173

Out of rods and cones m the retina of your eye:

which detect colour?

Q 13.1 | Page 269

Out of rods and cones m the retina of your eye:

which work in dim light?

Q 13.2 | Page 269

As light rays pass from water into glass, are they refracted towards the normal or away from the normal?

Q 14 | Page 220

State whether the following statement is true or false:
The image formed on our retina is upside-down

Q 14 | Page 269

Where is the image when you look at something in a mirror?

Q 14 | Page 173

A ray of light strikes a plane mirror such that its angle of incidence is 30°. What angle does the reflected ray make with the mirror surface?

Q 15 | Page 173

What is the principal function of the eye-lens?

Q 15 | Page 270

In which material do you think light rays travel faster-glass or air?

Q 15 | Page 220

Which phenomenon of light makes the water to appear shallower than it really is?

Q 16 | Page 220

Where does the greatest degree of refraction of light occur in the eye?

Q 16 | Page 270

What is the difference between a real image and a virtual image? Give one example of each type of image

Q 16 | Page 173

State whether the following statement is true or false:
Refraction occurs because light slows down in denser materials.

Q 17 | Page 220

What changes the shape of lens in the eye?

Q 17 | Page 270

The letter F is placed in front of a plane mirror:

How would its image look like when seen in a plane mirror?

Q 17.1 | Page 173

The letter F is placed in front of a plane mirror:

What is the name of the phenomenon involved?

Q 17.2 | Page 173

What is lateral inversion? Explain by giving a suitable example.

Q 18 | Page 173

Why does a ray of light bend when it travels from one medium to another?

Q 18 | Page 220

What do the ciliary muscles do when you are focusing on a nearby object?

Q 18 | Page 270

Write the word AMBULANCE as it would appear when reflected in a plane mirror. Why is it sometimes written in this way (as its mirror image) on the front of an ambulance?

Q 19 | Page 173

What is the least distance of distinct vision for a normal human eye?

Q 19 | Page 270

Fill in the following blank with suitable word:

Light travelling along a normal is ...............refracted.

Q 19.1 | Page 220

Fill in the following blank with suitable word:

Light bends when is passes from water into air. We say that it is ............

Q 19.2 | Page 220

What is meant by 'refraction of light'? Draw a labelled ray diagram to show the refraction of light.

Q 20 | Page 220

What are the important differences between looking at a photograph of your face and looking at yourself in a plane mirror?

Q 20 | Page 173

What is the:

far point of a normal human eye?

Q 20.1 | Page 270

What is the:

near point of a normal human eye?

Q 20.2 | Page 270

A ray of light travelling in air is incident on a rectangular glass block and emerges out into the air from the opposite face. Draw a labelled ray diagram to show the completer path of this ray of light. Mark the two points where the refraction of light takes place. What can you say about the final direction of ray of light?

Q 21 | Page 220

What is the range of vision of a normal human eye?

Q 21 | Page 270

A wall reflects light and a mirror also reflects light. What difference is three in the way they reflect light?

Q 21.1 | Page 173

Which type of reflection of light leads to the formation of images?

Q 21.2 | Page 173

Name the part of our eyes which helps us to focus near and distant objects in quick succession.

Q 22 | Page 270

Draw a labelled ray diagram to show how a ray of light is refracted when it passes:

from air into an optically denser medium.

Q 22.1 | Page 220

What is the difference between regular reflection of light and diffuse reflection of light?

Q 22.1 | Page 174

Draw a labelled ray diagram to show how a ray of light is refracted when it passes:

from an optically denser medium into air.

Q 22.2 | Page 220

What type of reflection of light takes place from:

(a) a cinema screen
(b) a plane mirror
(c) a cardboard
(d) still water surface of a lake

Q 22.2 | Page 174

Define the term "power of accommodation" of human eye.

Q 23 | Page 470

The diagram given alongside shows a ray of light entering a rectangular block of glass.

(a) Copy the diagram and draw the normal at the point of entry.
(b) Draw the approximate path of the ray of light through the glass block and out of the other side.

Q 23 | Page 220

What can  you see in a completely dark room? If you switch on an electric bulb in this dark room as a light source, explain how you could now see:
(a) the electric bulb
(b) a piece of white paper.

Q 23 | Page 174

Name the defect of vision which can be corrected by a converging lens. Show clearly by a ray diagram how the lens corrects the defect.

Q 23 | Page 279

Give the scientific names of the following parts of the eye:

carries signals from an eye to the brain.

Q 24.1 | Page 270

What is meant by the 'angle of incidence' and the 'angle of refraction' for a ray of light?

Q 24.1 | Page 220

A boy with a mouth 5 cm wide stands 2 m away from a plane mirror. Where is his image and how wide is the image of his mouth?

Q 24.1 | Page 174

Draw a labelled ray diagram to show the angle of incidence and the angle of refraction for a refracted ray of light.

Q 24.2 | Page 220

Give the scientific names of the following parts of the eye:

muscles which change the shape of the eye-lens.

Q 24.2 | Page 270

The boy walks towards the mirror at a speed of 1 m/s. At what speed does his image approach him?

Q 24.2 | Page 174

Give the scientific names of the following parts of the eye:

a hole in the middle of the iris.

Q 24.3 | Page 270

Fill in the following blank with suitable words:

When light is dim, the pupil becomes................

Q 24.4 | Page 270

Give the scientific names of the following parts of the eye:

a clear window at the front of the eye.

Q 24.4 | Page 270

Fill in the following blank with suitable word:

The iris controls the amount of................entering the eye.

Q 24.5 | Page 270

Give the scientific names of the following parts of the eye:

changes shape to focus a picture on the retina.

Q 24.5 | Page 270

Light travels more quickly through water than through glass.

Which is optically denser : water or glass?

Q 25.1 | Page 220

Fill in the following blank with suitable word:

Most of the refraction of light rays entering the eye occurs at the outer surface of the.............

Q 25.1 | Page 270

An extended object in the form of an arrow pointing upward has been placed in front of a plane mirror. Draw a labelled ray-diagram to show the formation of its image.

Q 25.1 | Page 174

State the uses of plane mirrors.

Q 25.2 | Page 174

Fill in the following blank with suitable word:

The part of eye sensitive to light is...................

Q 25.2 | Page 270

Light travels more quickly through water than through glass.

If a ray of light passes from glass into water, which way will it bend : towards the normal or away from the normal?

Q 25.2 | Page 220

Fill in the following blank with suitable word:

The part of eye which alters the size of the pupil is............

Q 25.3 | Page 270

Fill in the following blank with suitable word:

To bring light from a distant object to a focus on the retina of the eye, the convex eye-lens needs to be made..........

Q 25.6 | Page 270

Fill in the following blank with suitable word:

To bring light from a near object to a focus on the retina of the eye, the convex eye-lens need­ to be made....................

Q 25.7 | Page 270

Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

Q 26 | Page 270

What is meant by 'reflection of light'?

Q 26.1 | Page 174

Draw a labelled ray diagram to show how a ray of light passes through a parallel sided glass block:

if it hits the glass block at 90° (that is, perpendicular to the glass block)

Q 26.1 | Page 220

Draw a labelled ray diagram to show how a ray of light passes through a parallel sided glass block:

if it hits the glass block at an angle other than 90° (that is, obliquely to the glass block).

Q 26.2 | Page 220

Define the following terms used in the study of reflection of light by drawing a labelled ray-diagram:

(a) Incident ray
(b) Point of incidence
(c) Normal
(d) Reflected ray
(e) Angle of incidence
(f) Angle of reflection

Q 26.2 | Page 174

State and explain the laws of reflection of light at a plane surface (like a plane mirror), With the help of a labelled ray-diagram. Mark the angles of 'incidence' and 'reflection' clearly on the diagram. If the angle of reflection is 47.5°, what will be the angle of incidence?

Q 27 | Page 174

When a light ray passes from air into glass, what happens to its speed? Draw a diagram to show which way the ray of light bends.

Q 27 | Page 200

What changes take place in the shape of eye-lens:

when the eye is focused on a near object?

Q 27.1 | Page 270

What changes take place in the shape of eye-lens:

when the eye is focused on a distant object?

Q 27.2 | Page 270

With the help of a labelled ray-diagram, describe how a plane mirror forms an image of a point source of light placed in front of it. State the characteristics of the image formed in a plane mirror.

Q 28 | Page 174

The eyes of a person are focused (i) on a nearby object, and (ii) on a distant object, turn by turn. In which case:

the focal length of eye-lens will be the maximum?

Q 28.1 | Page 270

Explain why, a stick half immersed in water appears to be bent at the surface. Draw a labelled diagram to illustrate your answer.

Q 28.1 | Page 220

The eyes of a person are focused (i) on a nearby object, and (ii) on a distant object, turn by turn. In which case:

the converging power of eye-lens will be the maximum?

Q 28.2 | Page 270

A coin in a glass tumbler appears to rise as the glass tumbler is slowly filled with water. Name the phenomenon responsible for this effect.

Q 28.2 | Page 200

What change is made in the eye to enable it to focus on objects situated at different distances? Illustrate your answer with the help of diagrams.

Q 29 | Page 270

Explain why, though both a plane mirror and a sheet of paper reflect light but we can see the image of our face in a plane mirror but not in a sheet of paper.

Q 29.1 | Page 174

With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.

Q 29.1 | Page 220

The image in a plane mirror is virtual and laterally inverted. What does this statement mean?

Q 29.2 | Page 174

Name the phenomenon due to which a pencil partly immersed in water and held obliquely appears to be bent at the water surface.

Q 29.2 | Page 220

Write all the capital letters of the alphabet which look the same in a plane mirror.

Q 29.3 | Page 174

How is the amount of light entering the eye controlled?

Q 30 | Page 270

The angle of reflection is equal to the angle of incidence:

(a) always
(b) sometimes
(c) under special conditions
(d) never

Q 30 | Page 174

With the help of a diagram, show how when light falls obliquely on the side of a rectangular glass slab, the emergent ray is parallel to the incident ray.

Q 30.1 | Page 220

Show the lateral displacement of the ray on the diagram.

Q 30.1 | Page 220

State two factors on which the lateral displacement of the emergent ray depends.

Q 30.3 | Page 220

The angle between an incident ray and the plane mirror is 30°. The total angle between the incident ray and reflected ray will be:

(a) 30°
(b) 60°
(c) 90°
(d) 120°

Q 31 | Page 174

What happens to the eye when you enter a darkened cinema hall from bright sunshine? Give reason for your answer.

Q 31 | Page 270

Explain with the help of a labelled ray diagram, why a pencil partly immersed in water appears to be bent at the water surface. State whether the bending of pencil will increase or decrease if water is replaced by another liquid which is optically more dense than water. Give reason for your answer.

Q 31 | Page 220

A ray of light is incident on a plane mirror making an angle of 90° with the mirror surface. The angle of reflection for this ray of light will be:

(a) 45°
(b) 90°
(c) 0°
(d) 60°

Q 32 | Page 174

Light travelling from a denser medium to a rarer medium along a normal to the boundary:

(a) is refracted towards the normal
(b) is refracted away from the normal
(c) goes along the boundary
(d) is not refracted

Q 32 | Page 221

Why does it take some time to see objects in a dim room when you enter the room from bright sunshine outside?

Q 32 | Page 270

The image of an object formed by a plane mirror is:

(a) virtual
(b) real
(c) diminished
(d) upside-down

Q 33 | Page 174

A ray of light passes from glass into air. The angle of refraction will be:

(a) equal to the angle of incidence
(b) greater than the angle of incidence
(c) smaller than the angle of incidence
(d) 45°

Q 33 | Page 221

A person walking in a dark corridor enters into a brightly lit room:

State the effect on the pupil of the eye.

Q 33.1 | Page 271

How does this affect the amount of light entering the eye?

Q 33.2 | Page 271

The image formed by a plane mirror is :

(a) virtual, behind the mirror and enlarged.
(b) virtual, behind the mirror and of the same size as the object.
(c) real, at the surface of the mirror and enlarged.
(d) real, behind the mirror and of the same size as the object.

Q 34 | Page 174

A ray of light travelling in air goes into water. The angle of refraction will be:

(a) 90°
(b) smaller than the angle of incidence
(c) equal to the angle of incidence
(d) greater than the angle of incidence

Q 34 | Page 221

Ciliary muscles of human eye can contract or relax. How does it help in the normal functioning of the eye?

Q 34 | Page 271

The speed of light in air is:

(a) 3 × 108 cm/s
(b) 3 × 108 mm/s
(c) 3 × 108 km/s
(d) 3 × 108 m/s

Q 35 | Page 221

Describe and explain, how a normal eye can see objects lying at various distances clearly.

Q 35 | Page 271

The figure given alongside shows the image of a clock as seen a plane mirror. The correct time is:
Figure

(a) 2.25
(b) 2.35
(c) 6.45
(d) 9.25

Q 35 | Page 174

A man stands 10 m in front of a large plane mirror. How far must the walk before he is 5 m away from his image?

Q 36 | Page 174

When a ray of light travelling in glass enters into water obliquely:

(a) it is refracted towards the normal
(b) it is not refracted at all
(c) it goes along the normal
(d) it is refracted away from the normal

Q 36 | Page 221

There are two types of light-sensitive cells in the human eye:

Where are they found?

Q 36.1 | Page 270

There are two types of light-sensitive cells in the human eye:

What is each type called?

Q 36.2 | Page 271

There are two types of light-sensitive cells in the human eye:

To what is each type of cell sensitive?

Q 36.3 | Page 271

What are rods and cones in the retina of an eye? Why is our night vision relatively poor compared to the night vision of an owl?

Q 37 | Page 271

An object is placed 20 cm in front of a plane mirror. The mirror is moved 2 cm towards the object. The distance between the positions of the positions of the original and final images seen in the mirror is:

(a) 2 cm
(b) 4 cm
(c) 10 cm
(d) 22 cm

Q 37 | Page 175

A ray of light travelling in water falls at right angles to the boundary of a parallel-sided glass block. The ray of light:

(a) is refracted towards the normal
(b) is refracted away from the normal
(c) does not get refracted
(d) is reflected along the same path

Q 37 | Page 221

A man sits in an optician's chair looking into  plane mirror which is 2 m away from him and views the image of a chart which faces the mirror and is 50 cm behind his head. How far away from his eyes does the chart appear to be?

Q 38 | Page 175

A ray of light passes from a medium X to another medium Y. No refraction of light occurs if the ray of light hits the boundary of medium Y at an angle of:

(a) 0°
(b) 45°
(c) 90°
(d) 120°

Q 38 | Page 221

How does the convex eye-lens differ from the ordinary convex lens made of glass?

Q 38.1 | Page 271

List, in order, the parts of the eye through which light passes to reach the retina.

Q 38.2 | Page 271

A ray of light strikes a plane mirror PQ at an angle of incidence of 30°, is reflected from the plane mirror and then strikes a second plane mirror QR placed at right angles to the first mirror. The angle of reflection at the second mirror is:

(a) 30°
(b) 45°
(c) 60°
(d) 90°

Q 39 | Page 175

Which of the following diagrams shows the ray of light refracted correctly?

Q 39 | Page 221

What happens to the size of pupil of our eye (i) in dim light (ii) in bright light?

Q 39.1 | Page 271

Name the cells on the retina of an eye which are sensitive to (i) bright light (ii) dim light (iii) sensation of colour.

Q 39.2 | Page 271

Explain how to read the following message which was found on some blotting paper:

Q 40 | Page 175

Draw a simple diagram of the human eye and label clearly the cornea, iris, pupil, ciliary muscles, eye-lens, retina, optic nerve and blind spot.

Q 40.1 | Page 271

A vertical ray of light strikes the horizontal surface of some water:

What is the angle of incidence?

Q 40.1 | Page 221

Describe the working of the human eye with the help of the above diagram.

Q 40.2 | Page 271

A vertical ray of light strikes the horizontal surface of some water:

What is the angle of refraction?

Q 40.2 | Page 221

How does the eye adjust itself to deal with light of varying intensity?

Q 40.3 | Page 171

Explain the functions of the following parts of the eye:
(i) cornea
(ii) iris
(iii) pupil
(iv) ciliary muscles
(v) eye-lens

Q 41.1 | Page 271

If you walk from a dark room into sunlight and back again into dark room, how would your pupils alter in size? What makes this happen?

Q 41.2 | Page 271

Explain why, we cannot see our seats first when we enter a darkened cinema hall from bright light but gradually they become visible.

Q 41.3 | Page 271

The human eye forms the image of an object at its:
(a) cornea
(b) iris
(c) pupil
(d) retina

Q 42 | Page 271

How does the light have to enter the glass:

to produce a large amount of bending?

Q 42.1 | Page 221

How does the light have to enter the glass:

for no refraction to happen?

Q 42.2 | Page 221

The change in focal length of an eye-lens is caused by the action of the:
(a) pupil
(b) retina
(c) ciliary muscles
(d) iris

Q 43 | Page 271

How can you bend light away from the normal?

Q 43.1 | Page 221

How must light travel out of a substance if it is not going to be refracted?

Q 43.2 | Page 221

Draw and complete the following diagrams to show what happens to the beams of light as they enter the glass block and then leave it:

Q 44 | Page 221

The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m

Q 44 | Page 271

Refraction of light in the eye occurs at:
(a) the lens only
(b) the cornea only
(c) both the cornea and the lens
(d) the pupil

Q 45 | Page 271

Why does a beam of light when it enters glass at an angle? Why does it not bend if it inters the glass at right angles?

Q 45 | Page 221

To focus the image of a nearby object on the retina of an eye:
(a) the distance between eye-lens and retina is increased
(b) the distance between eye-lens and retina is decreased
(c) the thickness of eye-lens is decreased
(d) the thickness of eye-lens is increased

Q 46 | Page 271

The term " accommodation" as applied to the eye, refers to its ability to:
(a) control the light intensity falling on the retina
(b) erect the inverted image formed on the retina
(c) vary the focal length of the lens
(d) vary the distance between the lens and retina

Q 47 | Page 271

Which of the following controls the amount of light entering the eye?
(a) ciliary muscles
(b) lens
(c) iris
(d) cornea

Q 48 | Page 271

The human eye possesses the power of accommodation. This is the power to:
(a) alter the diameter of the pupil as the intensity of light changes
(b) distinguish between lights of different colours
(c) focus on objects at different distances
(d) decide which of the two objects is closer.

Q 49 | Page 272

How does the eye change in order to focus on near or distant objects?
(a) The lens moves in or out
(b) The retina moves in or out
(c) The lens becomes thicker or thinner
(d) The pupil gets larger or smaller

Q 50 | Page 272

Which of the following changes occur when you walk out of bright sunshine into a poorly lit room?
(a) the pupil becomes larger
(b) the lens becomes thicker
(c) the ciliary muscle relaxes
(d) the pupil becomes smaller

Q 51 | Page 272

The size of the pupil of the eye is adjusted by:
(a) cornea
(b) ciliary muscles
(c) optic nerve
(d) iris

Q 52 | Page 272

The descriptions of five kinds of images are given below:
(a) diminished and virtual
(b) enlarged and real
(c) enlarged and erect
(d) real and inverted
(e) virtual and the same size
Which one of these describes the image formed:
(i) on the retina of the eye?
(ii) by a magnifying glass?
(iii) by a convex driving mirror on a car?
(iv) by a plane mirror?
(v) on the screen of a slide projector?

Q 53 | Page 272

when you look at your hand?

Q 54.1 | Page 272

when you look at a distant tree?

Q 54.2 | Page 272

Suggest how your irises help to protect the retinas of your eyes from damage by bright light.

Q 55 | Page 272

Which parts of the eye cause rays of light to converge on the retina?

Q 56 | Page 272

Which part causes the greatest convergence?

Q 56.2 | Page 272

Which part brings the image into sharp focus on the retina? How does it do this?

Q 56.3 | Page 272

An object is moved closer to an eye. What changes must take place in the eye in order to keep the image in sharp focus?

Q 57 | Page 272

Why does the eye-lens not have to do all the work of converging incoming light rays?

Q 58 | Page 272

Explain why, when it is getting dark at night, it is impossible to make out the colour of cars on the road.

Q 59 | Page 272

Nocturnal animals (animals which sleep during the day and come out at night) tend to have  wide pupils and lot of rods in their retinas. Suggest reasons for this.

Q 60 | Page 272

#### Pages 178 - 281

Name one of the common defects of vision and the type of lens used to remove it.

Q 1 | Page 279

Name the spherical mirror which has:

(a) virtual principal focus.
(b) real principal focus.

Q 1 | Page 178

What name is given to the ratio of sine of angle of incidence to the sine of angle of refraction?

Q 1 | Page 227

Write the relation between the angle of incidence and the angle of refraction for a medium.

Q 2 | Page 227

Out of convex mirror and concave mirror, whose focus is situated behind the mirror?

Q 2 | Page 178

Name the defect of vision in a person:

whose near point is more than 25 on away.

Q 2.1 | Page 279

Name the defect of vision in a person:

whose far point is less than infinity

Q 2.2 | Page 279

What is the unit of refractive index?

Q 3 | Page 228

Find the focal length of a concave mirror whose radius of curvature is 32 cm.

Q 3 | Page 178

Which defect of vision can be rectified:

by using a concave lens?

Q 3.1 | Page 279

Which defect of vision can be rectified:

by using a convex lens?

Q 3.2 | Page 279

If the focal length of a convex mirror is 25 cm, what is its radius of curvature?

Q 4 | Page 178

Which has higher refraction index :  water of glass?

Q 4 | Page 228

What type of lens is used to correct

myopia?

Q 4.1 | Page 279

What type of lens is used to correct

hypermetropia

Q 4.2 | Page 279

Refractive indices of carbon disulphide and ethyl alcohol are 1.63 and 1.36 respectively. Which is optically denser?

Q 5 | Page 228

What is the other name for

myopia

Q 5.1 | Page 279

Fill in the following blank with suitable word:

Parallel rays of light are reflected by a concave mirror to a point called the ..........

Q 5.1 | Page 179

Fill in the following blank with suitable word:

The focal length of a concave mirror is the distance from the ......... to the mirror.

Q 5.2 | Page 179

What is the other name for

hypermetropia

Q 5.2 | Page 279

Fill in the following blank with suitable word:

A concave mirror .......... rays of light whereas convex mirror ............ rays

Q 5.3 | Page 179

ill in the following blank with suitable word:

For a convex mirror, parallel rays of light appear to diverge from a point called the ......... .

Q 5.4 | Page 179

The refractive index of diamond is 2.42. What is the meaning of this statement in relation to the speed of light?

Q 6 | Page 228

What is a spherical mirror? Distinguish between a concave mirror and a convex mirror.

Q 6 | Page 179

What is the scientific name of

short-sightedness

Q 6.1 | Page 279

What is the scientific name of

long-sightedness?

Q 6.2 | Page 279

If the refractive index for light going from air to diamond be 2.42, what will be the refractive index from light going from diamond to air?

Q 7 | Page 228

Name the two types of spherical mirrors. What type of mirror is represented by the:

back side of a shining steel spoon?

Q 7.1 | Page 179

What kind of lens is used to correct

short-sightedness

Q 7.1 | Page 279

Name the two types of spherical mirrors. What type of mirror is represented by the:

front side of a shining steel spoon?

Q 7.2 | Page 179

What kind of lens is used to correct

long-sightedness?

Q 7.2 | Page 279

What is the relation between the focal length and radius of curvature of a spherical mirror (concave mirror of convex mirror)? Calculate the focal length of a spherical mirror whose radius of curvature is 25 cm.

Q 8 | Page 179

How is the refractive index of a material related to the speed of light in it?

Q 8 | Page 228

State whether the following statement is true or false:
Short-sightedness can be cured by using a concave lens.

Q 8 | Page 279

Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.

Q 9 | Page 279

Explain with a suitable diagram, how a concave mirror converges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of concave mirror in this diagram.

Q 9 | Page 179

Fill in the following blank with a suitable word:
When a ray of light goes from air into a clear material, you see the ray bend. How much the ray bends is determined by the ............... of the material.

Q 9 | Page 228

Give three examples of materials that refract light rays. What happens to the speed of light rays when they enter these materials?

Q 10 | Page 228

Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.

Q 10 | Page 279

Describe with a suitable diagram, how a convex mirror diverges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of concave mirror in this diagram.

Q 10 | Page 179

Define Snell's law of refraction. A ray of light is incident on a glass slab at an angle of incidence of 60°. If the angle of refraction be 32.7°, calculate the refractive index of glass. (Given : sin 60° = 0.866, and sin 32.7° = 0.540).

Q 11 | Page 228

Define (a) centre of curvature (b) radius of curvature (c) pole (d) principal axis, and (e) aperture, of a spherical mirror with the help of a labelled diagram

Q 11 | Page 179

What is the other name of old age hypermetropia?

Q 11 | Page 279

Name any two defects of vision which can be corrected by using spectacles.

Q 12 | Page 279

The speed of light in vacuum and in two different glasses is given in the table below:

 Medium Speed of light Vacuum 3.00 × 108 m/s Flint glass 1.86 × 108 m/s Crown glass 1.97 × 108 m/s

(a) Calculate the absolute refractive indexes of flint glass and crown glass.
(b) Calculate the relative refractive index for light going from crown glass to flint glass.

Q 12 | Page 228

Define (i) principal focus of a concave mirror, and (ii) focal length of a concave mirror.

Q 12.1 | Page 179

Draw diagram to represent the action of a concave mirror on a beam of parallel light rays. Mark on this diagram principal axis, focus F, centre of curvature C, pole P and focal length f, of the concave mirror.

Q 12.2 | Page 179

The speed of light in air is 3 × 108 m/s. In medium X its speed is 2 × 108 m/s and in medium Y the speed of light is 2.5 × 108 m/s Calculate:

(aair nx
(bair nY
(cx n

Q 13 | Page 228

Name one defect of vision (or eye) which cannot be corrected by any type of spectacle lenses.

Q 13 | Page 279

What is meant by (i) principal focus of a convex mirror, and (ii) focal length of a convex mirror?

Q 13.1 | Page 179

Draw diagram to show the action of convex mirror on a beam of parallel light rays. Mark on this diagram principal axis, focus F, centre of curvature C, pole P and focal length f, of the convex mirror.

Q 13.2 | Page 179

What is the speed of light in a medium of refractive index 6/5 if its speed in air is 3,00,000 km/s?

Q 14 | Page 228

In a convex spherical mirror, reflection of light takes place at:

(a) a flat surface
(b) a bent-in surface
(c) a bulging-our surface
(d) an uneven surface

Q 14 | Page 179

Name the body part with which the terms myopia and hypermetropia are connected.

Q 14 | Page 279

What is the far point of a person suffering from myopia (or short-sightedness)?

Q 15 | Page 279

A diverging mirror is

(a) a plane mirror
(b) a convex mirror
(c) a concave mirror
(d) a shaving mirror

Q 15 | Page 179

The speed of light in water is 2.25 × 108 m/s. If the speed of light in vacuum be 3 × 108 m/s, calculate the refractive index of water.

Q 16 | Page 228

Where is the near point of a person suffering from hypermetropia (or long-sightedness)?

Q 16 | Page 279

If R is the radius of curvature of a spherical mirror and f is its focal length, then:

(aR = f
(bR = 2f
(c) R = f/2
(dR = 3f

Q 16 | Page 179

The focal length of a spherical mirror of radius of curvature 30 cm is:

(a) 10 cm
(b) 15 cm
(c) 20 cm
(d) 30 cm

Q 17 | Page 179

Light enters from air into diamond which has a refractive index of 2.42. Calculate the speed of light in diamond. The speed of light in air is 3.0 × 108 ms−1

Q 17 | Page 228

Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.

Is she short-sighted or long-sighted?

Q 17.1 | Page 279

Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.

What type of lenses-converging or diverging-would an optician prescribe for her?

Q 17.2 | Page 279

If the focal length of a spherical mirror is 12.5 cm, its radius of curvature will be:

(a) 25 cm
(b) 15 cm
(c) 20 cm
(d) 35 cm

Q 18 | Page 179

A man can read the number of a distant but clearly but he finds difficulty in reading a book.

From which defect of the eye is he suffering?

Q 18.1 | Page 279

State and explain the laws of refraction of light with the help of a labelled diagram.

Q 18.1 | Page 228

A man can read the number of a distant but clearly but he finds difficulty in reading a book.

What type of spectacle lens should he use to correct the  defect?

Q 18.2 | Page 279

What is meant by the refractive index of a substance?

Q 18.2 | Page 228

Light travels through air at 300 million ms−1. On entering water it slows down to 225 million ms−1. Calculate the refractive index of water.

Q 18.3 | Page 228

The refractive indices of four substance P, Q, R and S are 1.50, 1.36, 1.77 and 1.31 respectively. The speed of light is the maximum in the substance:

(aP
(bQ
(cR
(d

Q 19 | Page 228

A communications satellite in orbit sends a parallel beam of signals down to earth. If these signals obey the same laws of reflection as light and are to be focussed onto a small receiving aerial, what should be the best shape of the metal 'dish' used to collect them?

Q 19 | Page 179

A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.

Name the type of defect he is suffering from.

Q 19.1 | Page 279

A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.

How can this defect by corrected?

Q 19.2 | Page 279

The refractive indices of four materials A, B, C and D are 1.33, 1.43, 1.71 and 1.52 respectively. When the light rays pass from air into these materials, they refract the maximum in:

(a) material A
(b) material B
(c) material C
(d) material D

Q 20 | Page 228

Complete the following sentence:

A short-sighted person cannot see ............ objects clearly. Short-sightedness can be corrected by using ........... lenses.

Q 20.1 | Page 279

When a spherical mirror is held towards the sun and its sharp image is formed on a piece of a carbon paper for some time, a hole is burnt in the carbon paper.

What is the nature of spherical mirror?

Q 20.1 | Page 179

Complete the following sentence.

A long-sighted person cannot see ........... objects clearly. Long-sightedness can be corrected by using .............. lenses.

Q 20.2 | Page 279

When a spherical mirror is held towards the sun and its sharp image is formed on a piece of a carbon paper for some time, a hole is burnt in the carbon paper.

Why is a hole burnt in the carbon paper?

Q 20.2 | Page 179

When a spherical mirror is held towards the sun and its sharp image is formed on a piece of a carbon paper for some time, a hole is burnt in the carbon paper.

At which point of the spherical mirror the carbon paper is placed?

Q 20.3 | Page 179

When a spherical mirror is held towards the sun and its sharp image is formed on a piece of a carbon paper for some time, a hole is burnt in the carbon paper.

What name is given to the distance between spherical mirror and carbon paper?

Q 20.4 | Page 179

When a spherical mirror is held towards the sun and its sharp image is formed on a piece of a carbon paper for some time, a hole is burnt in the carbon paper.

What is the advantage of using a carbon paper rather than a white paper?

Q 20.5 | Page 179

The refractive index of glass for light going from air to glass is  The refractive index for light going from glass to air will be:

(a) 1/3

(b) 4/5
(c) 4/6
(d) 5/2

Q 21 | Page 229

What are the two most common defects of vision (or defects of eye)? How are they corrected?

Q 21 | Page 279

Differentiate between myopia and hypermetropia. What type of spectacles should be worn by a person having the defects of myopia as well as hypermetropia? How does it help?

Q 22 | Page 279

The refractive index of glass for light going from air to glass is .

The refractive index for light going from glass to air will be:

(a) 1/3

(b) 4/5
(c) 4/6
(d) 5/2

Q 22 | Page 229

The speed of light in substance X is 1.25 × 108 m/s and that in air is 3 × 108 m/s. The refractive index of this substance will be:

(a) 2.4
(b) 0.4
(c) 4.2
(d) 3.75

Q 23 | Page 229

Describe with the help of a ray diagram the nature, size and position of the image formed when an object is placed at infinity (considerable distance) in front of a convex lens. State three characteristics of the image so formed.

Q 24 | Page 240

The refractive indexes of four substances P, Q, R and S are 1.77, 1.50, 2.42 and 1.31 respectively. When light travelling in air is incident on these substances at equal angles, the angle of refraction will be the maximum in:

(a) substance P
(b) substance Q
(c) substance R
(d) substance S

Q 24 | Page 229

Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defect.

Q 24 | Page 280

The refractive index of water is:

(a) 1.33
(b) 1.50
(c) 2.42
(d) 1.36

Q 25 | Page 229

Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.

Q 25 | Page 280

Explain with the help of labelled ray-diagram, the defect of vision called hypermetropia, and hot it is corrected by a lens.

Q 26 | Page 280

The refractive index of water with respect to air is 4/3. The refractive index of air with respect to water will be:

(a) 1.75
(b) 0.50
(c) 0.75
(d) 0.25

Q 26 | Page 229

Refractive indices of water, sulphuric acid, glass and carbon disulphide are 1.33, 1.43, 1.53 and 1.63 respectively. the light travels slowest in:

(a) sulphuric acid
(b) glass
(c) water
(d) carbon disulphide

Q 27 | Page 229

A person suffering from the eye-defect myopia (short-sightedness) can see clearly only up to a distance of 2 metres. What is the nature and power of lens required to rectify this defect?

Q 27 | Page 280

The refractive index of glass with respect to air is 3/2 and the refractive index of water with respect to air is 4/3. The refractive index of glass with respect to water will be:

(a) 1.525
(b) 1.225
(c) 1.425
(d) 1.125

Q 28 | Page 229

The near-point of a person suffering from hypermetropia is at 50 cm from his eye. What is the nature and power of the lens needed to correct this defect? (Assume that the near-point of the normal eye is 25 cm).

Q 28 | Page 280

A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?

Q 29 | Page 280

The following table gives the refractive indices of a few media:

 1 2 3 4 5 Medium Water Crown glass Rock salt Ruby Diamond Refractive index 1.33 1.52 1.54 1.71 2.42

Use this table to give an example of:

(i) a medium pair so that light speeds up when it goes from one of these medium to another.
(ii) a medium pair so that light slows down when it goes from one of these medium to another.

Q 29 | Page 229

Refractive indices of four media A, B, C and D are given below:

 Medium Refractive index A 1.33 B 1.44 C 1.52 D 1.65

In which of these four media is the speed of light (i) maximum, and (ii) minimum?

Q 30 | Page 229

What is presbyopia? Write two causes of this defect. Name the type of lens which can be used to correct presbyopia.

Q 30 | Page 280

When is a person said to have developed cataract in his eye? How is the vision of a person having cataract restored?

Q 31 | Page 280

fill in the following blank with suitable word:
A person is short-sighted if his eyeball is too............Spectacles with a .............lens are needed. A person is long-sighted if his eyeball is too............Spectacles with a ................lens are needed. These focus light rays exactly on to the..........

Q 32 | Page 280

What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.

Q 33.1 | Page 280

A person having short-sight cannot see objects clearly beyond a distance of 1.5 m. What would be the nature and power of the corrective lens to restore proper vision?

Q 33.2 | Page 280

What is long-sightedness? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show:
(i) the eye-defect long-sightedness.
(ii) correction of long-sightedness by using a lens.

Q 34.1 | Page 280

An eye has a near point distance of 0.75 m. What sort of lens in spectacles would be needed to reduce the near point distance to 0.25 m? Also calculate the power of lens required. Is this eye long-sighted or short-sighted?

Q 34.2 | Page 280

An eye has a far point of 2 m. What type of lens in spectacles would be needed to increase the far point to infinity?  Also calculate the power of lens required. Is this eye long-sighted or short-sighted?

Q 34.3 | Page 280

The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(d) hypermetropia

Q 36 | Page 280

A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia

Q 37 | Page 280

Though a woman can see the distant object clearly, she cannot see the nearby objects clearly. She is suffering from the defect of vision called:
(a) long-sight
(b) short-sight
(c) hind-sight
(d) mid-sight

Q 38 | Page 280

A young man has to hold a book at arm's length to be able to read it clearly. The defect of vision is:
(a) astigmatism
(b) myopia
(c) presbyopia
(d) hypermetropia

Q 39 | Page 280

After testing the eyes of a child, the optician has prescribed the following lenses for his spectacles:
Left eye : + 2.00 D
Right eye : + 2.25 D
The child is suffering from the defect of vision called:
(a) short-sightedness
(b) long-sightedness
(c) cataract
(d) presbyopia

Q 40 | Page 281

A person got his eyes tested. The optician's prescription for the spectacles reads:
Left eye: − 3.00 D
Right eye: − 3.50 D
The person is having a defect of  vision called:
(a) presbyopia
(b) myopia
(c) astigmatism
(d) hypermetropia

Q 41 | Page 281

A student sitting on the last bench in the class cannot read the writing on the blackboard clearly but he can read the book lying on his desk clearly. Which of the following statement is correct about the student?
(a) The near point of his eyes has receded away.
(b) The near point of his eyes has come close to him.
(c) The far point of his eyes has receded away.
(d) The far point of his eyes has come closer to him.

Q 42 | Page 281

A man driving a car can read a distant road sign clearly but finds difficulty in reading the odometer on the dashboard of the car. Which of the following statement is correct about this man?
(a) The near point of his eyes has receded away.
(b) The near point of his eyes has come closer to him.
(c) The far point of his eyes has receded away.
(d) The far point of his eyes has come closer to him.

Q 43 | Page 281

The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
(a) myopia
(b) presbyopia
(c) colourblindness
(d) cataract

Q 44 | Page 281

A person cannot see distant objects clearly. His vision can be corrected by using the spectacles containing:
(a) concave lenses
(b) plane lenses
(c) contact lenses
(d) convex lenses

Q 45 | Page 281

A person finds difficulty in seeing nearby objects clearly. His vision can be corrected by using spectacles containing:
(a) converging lenses
(b) diverging lenses
(c) prismatic lenses
(d) chromatic lenses

Q 46 | Page 281

In a certain murder investigation, it was important to discover whether the victim was long-sighted or short-sighted. How could a detective decide by examining his spectacles?

Q 47 | Page 281

The picture given here shows a person wearing 'half-moon' spectacles. What sort of eye-defect do do you think he has? Why are these particular spectacles useful to him?

Q 48 | Page 281

A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of:
(i) 5 cm?
(ii) 25 cm?
(iii) 50 cm?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need?

Q 49 | Page 281

The near point of a long-sighted person is 50 cm from the eye.
(a) Can she see clearly an object at:
(i) a distance of 20 cm?
(ii) at infinity?

Q 50.1 | Page 281

To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?

Q 50.2 | Page 281

A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:
if the person is an old man

Q 51.1 | Page 281

A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:

if the person is a young man

Q 51.2 | Page 281

#### Pages 189 - 288

For what position of an object, a concave mirror forms a real image equal in size to the object?

Q 1 | Page 189

Name the lens which can concentrate sun's rays to a point and burn a hole in a piece of paper.

Q 1 | Page 239

How much is our field of view:

with one eye open?

Q 1.1 | Page 283

How much is our field of view:

with both eyes open?

Q 1.2 | Page 283

Where should an object be placed in front of the concave mirror so as to obtain its virtual, erect and magnified image?

Q 2 | Page 189

Give the usual name for the following:
A point inside a lens through which the light passes undeviated.

Q 2 | Page 239

Which of the following have a wider field of view?
(a) Animals having two eyes on the opposite sides of their head.
(b) Animals having two eyes at the front of their head.

Q 2 | Page 283

Which type of mirror has:

positive focal length?

Q 2.1 | Page 191

For which positions of the object does a concave mirror produce an inverted, magnified an real image?

Q 3 | Page 189

A 1 cm high object is placed at a distance of 2f from a convex lens. What is the height of the image formed?

Q 3 | Page 239

Out of animals of prey and predators, which have their eyes:

at the front of their head?

Q 3.1 | Page 283

Out of animals of prey and predators, which have their eyes:

on the opposite sides of their head?

Q 3.2 | Page 283

f the image formed by a convex lens is of the same size as that of the object, what is the position of the image with respect to the lens?

Q 4 | Page 239

State whether the following statement is true or false:
Rabbit has eyes which look sideways.

Q 4 | Page 283

If an object is placed at the focus of a concave mirror, where is the image formed?

Q 4 | Page 189

If an object is placed at the focus of a convex lens, where is the image formed?

Q 5 | Page 239

If an object is at infinity (very large distance) in front of a concave mirror, where is the image formed?

Q 5 | Page 189

Fill in the following blank with suitable word:

Having two eyes gives a ................field of view.

Q 5.1 | Page 284

Fill in the following blank with suitable word:

Having two eyes enables us to judge.................more accurately.

Q 5.2 | Page 284

Where should an object be placed in order to use a convex lens as a magnifying glass?

Q 6 | Page 239

For what position of an object, a real and diminished image is formed by a concave mirror?

Q 6 | Page 189

What are the advantages of having two eyes instead of just one?

Q 6 | Page 284

Where should an object be placed in front of a convex lens so as to obtain its virtual, erect and magnified image?

Q 7 | Page 239

Explain clearly why, a person who has lost the sight of one eye is at a disadvantage compared with the normal person who has two good eyes.

Q 7 | Page 284

Copy this figure in your answer book and show the direction of the light ray after reflection:

Q 7 | Page 189

Draw the following diagram in your answer book and show the formation of image of the object AB with the help of suitable rays:

Q 8 | Page 189

Where should an object be placed in front of a convex lens so as to obtain its real, inverted and magnified image?

Q 8 | Page 239

Name two animals having eyes:

one the sides of the head.

Q 8.1 | Page 284

Name two animals having eyes:

at the front of the head.

Q 8.2 | Page 284

Among animals, the predators (like lions) have their eyes facing forward at the front of their heads, whereas the animals of prey (like rabbit) usually have eyes at the sides of their head. Why is this so?

Q 9 | Page 284

Draw the following diagram in your answer book and show the formation of image with the help of suitable rays:

Q 9 | Page 189

For what position of an object a real, diminished image is formed by a convex lens?

Q 9 | Page 239

Which type of mirror could be used as a dentist's mirror?

Q 10 | Page 189

If an object is at a considerable distance (or infinity) in front of a convex lens, where is the image formed?

Q 10 | Page 239

Five persons A, B, C, D and E have diabetes, leukaemia, asthma, meningitis and hepatitis, respectively.

Which of these persons can donate eyes?

Q 10.1 | Page 284

Five persons A, B, C, D and E have diabetes, leukaemia, asthma, meningitis and hepatitis, respectively.

Which of these persons cannot donate eyes?

Q 10.2 | Page 284

Draw the given diagram in your answer book and complete it for the path of a ray of light after passing through the lens.

Q 11 | Page 240

Which kind of mirror is used in the headlights of a car? Why is it used for this purpose?

Q 11 | Page 189

The animal which does not have eyes that look sideways is:
(a) Horse
(b) Chicken
(c) Lion
(d) Fish

Q 11 | Page 284

What type of lens would you use as a magnifying glass? How close  must the object be to the lens?

Q 12 | Page 240

With both eyes open, a person's field of view is about:
(a) 90°
(b) 150°
(c) 180°
(d) 360°

Q 12 | Page 284

Explain why, a ray of light passing through the centre of curvature of a concave mirror gets reflected back along the same path.

Q 12 | Page 189

What is the minimum number of rays required for locating the image formed by a concave mirror for an object? Draw a ray diagram to show the formation of a virtual image by a concave mirror.

Q 13 | Page 189

Having two eyes gives a person:
(a) deeper field of view
(b) coloured field of view
(c) rear field of view
(d) wider field of view

Q 13 | Page 284

Name two factors on which the focal length of a lens depends.

Q 13 | Page 240

State any two uses of convex lenses.

Q 14 | Page 240

The animals of prey have:
(a) two eyes at the front
(b) two eyes at the back
(c) two eyes on the sides
(d) one eye at the front and one on the side

Q 14 | Page 284

With the help of a ray diagram, determine the position, nature and size of the image formed of an object placed at the centre of curvature of a concave mirror.

Q 14 | Page 189

Described with the help of a diagram, the nature, size and position of the image formed when an object is placed beyond the centre of curvature of a concave mirror.

Q 15 | Page 189

The animals called predators have:
(a) both the eyes on the sides
(b) one eye on the side and one at the front
(c) one eye on the front and one at the back
(d) both the eyes at the front

Q 15 | Page 284

Fill in the following blank with suitable word:

Parallel rays of light are refracted by a convex lens to a point called the ........

Q 15.1 | Page 240

Fill in the following blank with suitable word:

The image in a convex lens depends upon the distance of the ........... from the lens.

Q 15.2 | Page 240

If an object is placed at a distance of 8 cm from a concave mirror of focal length 10 cm, discuss the nature of the image formed by drawing the ray diagram.

Q 16 | Page 189

(i) A ray of white light breaks up into its components while passing through a glass prism. Draw a ray diagram to show the path of rays.
(ii) Mark the least deviated colour in your  diagram

(iii) Why do different coloured rays deviate differently in a prism?

Q 16 | Page 288

What is a lens?

Q 16.1 | Page 240

Distinguish between a convex lens and concave lens. Which of the two is a converging lens : convex lens of concave lens?

Q 16.2 | Page 240

Draw a ray diagram showing how a concave mirror can be used to produce a real, inverted and diminished image of an object.

Q 17 | Page 189

Explain with the help of a diagram, why the convex lens is also called a converging lens.

Q 17.1 | Page 240

Define principal axis, principal focus and focal length of a convex lens.

Q 17.2 | Page 240

Which mirror is used as a torch reflector? Draw a labelled diagram to show how a torch reflector can be used to produce a parallel beam of light. Where is the bulb placed in relation to the torch reflector?

Q 18 | Page 190

Explain with the help of a diagram, why the concave lens is also called a diverging lens.

Q 18.1 | Page 240

Define the principal focus of a concave lens.

Q 18.2 | Page 240

State where an object must be placed so that the image formed by a concave mirror is:

(a) erect and virtual.
(b) at infinity.
(c) the same size as the object.

Q 19 | Page 190

Draw a ray diagram to show the formation of a real magnified image by a convex lens. (In your sketch the position of object and image with respect to the principal focus of lens should be shown clearly).

Q 19 | Page 240

With the help of a labelled ray diagram, describe how a converging mirror can be used to give an enlarged upright image of an object.

Q 20 | Page 190

Describe with the help of a ray-diagram, the formation of image of a finite object placed in front of convex lens between f and 2f. Give two characteristics of the image so formed.

Q 20 | Page 240

Describe with the help of a ray diagram the nature, size and position of the image formed when an object is placed in front of a convex lens between focus and optical centre. State three characteristics of the image formed.

Q 21 | Page 240

Make labelled ray diagrams to illustrate the formation of:

a real image by a converging mirror.

Q 21.1 | Page 190

Make labelled  ray diagrams to illustrate the formation of:

a virtual image by a converging mirror.
Mark clearly the pole, focus, centre of curvature and position of object in each case.

Q 21.2 | Page 190

An object is placed at a distance equal to 2f in front of a convex lens. Draw a labelled ray diagram to show the formation of image. State two characteristics of the image formed.

Q 22 | Page 240

Briefly describe how you would find the focal length of a concave mirror quickly but approximately

Q 22 | Page 190

Describe with the help of a ray-diagram, the size, nature and position of the image formed by a convex lens when an object is placed beyond 2f in front of the lens.

Q 23 | Page 240

Which type of mirror is used in a solar furnace? Support your answer with reason.

Q 23 | Page 190

Name the type of mirror used by dentists. How does it help?

Q 24 | Page 190

Explain why, concave mirrors are used as shaving mirrors.

Q 25 | Page 190

What type of lens is shown in the diagram on the right? What will happen to the parallel rays of light? Show by completing the ray diagram.

Q 25.1 | Page 240

You eye contains a convex lens. Why is it unwise to look at the sun?

Q 25.2 | Page 240

Give two uses of concave mirrors. Explain why you would choose concave mirrors for these uses.

Q 26 | Page 190

Where must the object be placed for the image formed by a converging lens to be:

real, inverted and smaller than the object?

Q 26.1 | Page 240

Where must the object be placed for the image formed by a converging lens to be:

real, inverted and larger than the object?

Q 26.3 | Page 240

Where must the object be placed for the image formed by a converging lens to be:

real, inverted and same size as the object?

Q 26.4 | Page 240

Where must the object be placed for the image formed by a converging lens to be:

virtual, upright and larger than the object?

Q 26.4 | Page 240

Draw a diagram to show how a converging lens held close to the eye acts as a magnifying glass. Why is it usual to choose a lens of short focal length for this purpose rather than one of long focal length?

Q 27 | Page 240

Draw ray-diagrams to show the formation of images when the object is places in front of a concave mirror (converging mirror):

(i) between its pole and focus
(ii) between its centre of curvature and focus

Q 27.1 | Page 190

between its pole and focus

Describe the nature, size and position of the image formed in each case.

State one use of concave mirror bases on the formation of image as in case (i) above.

Q 27.2 | Page 190

How could you find the focal length of a convex lens rapidly but approximately?

Q 28 | Page 240

Give two circumstances in which a concave mirror can form a magnified image of an object placed in front of it. Illustrate your answer by drawing labelled ray diagrams for both.

Q 28.1 | Page 190

Which one of these circumstances enables a concave mirror to be used as a shaving mirror?

Q 28.2 | Page 190

The real image formed by a concave mirror is larger than the object when object is:

(a) at a distance equal to radius of curvature
(b) at a distance less than the focal length
(c) between focus and centre of curvature
(d) at a distance greater than radius of curvature

Q 29 | Page 190

With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the convex lens on the diagram.

Q 29.1 | Page 240

State whether convex lens has a real focus or a virtual focus.

Q 29.2 | Page 240

List some things that convex lens and concave mirror have in common.

Q 29.3 | Page 240

The real image formed by a concave mirror is smaller than the object if the object is:

(a) between centre of curvature and focus
(b) at a distance greater than radius of curvature
(c) at a distance equal to radius of curvature
(d) at a distance equal to focal length

Q 30 | Page 190

With the help of a labelled diagram, explain how a concave lens diverges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the concave lens on the diagram.

Q 30.1 | Page 241

State whether concave lens has a real focus or a virtual focus.

Q 30.2 | Page 241

List some things that concave lens and concave mirror have in common.

Q 30.3 | Page 241

The image formed by a concave mirror is virtual, erect and magnified. The position of object is:

(a) at focus
(b) between focus and centre of curvature
(c) at pole
(d) between pole and focus

Q 31 | Page 190

Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed:

at 2F1

Q 31.1 | Page 241

Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed:

between F1 and the optical centre O of the lens.
Which of the above two cases shows the use of convex lens as a magnifying glass? Give reasons for your choice.

Q 31.2 | Page 241

The image formed by a concave mirror is real, inverted and of the same size as the object. The position of the object must then be:

(a) at the focus
(b) between the centre of curvature and focus
(c) at the centre of curvature
(d) beyond the centre of curvature

Q 32 | Page 190

An object is placed well outside the principal focus of a convex lens. Draw a ray diagram to show how the image is formed, and say whether the image is real or virtual.

Q 32.1 | Page 241

What is the effect on the size and position of the image of moving the object (i) towards the lens, and (ii) away from the lens?

Q 32.2 | Page 241

The image formed by a concave mirror is real, inverted and highly diminished (much smaller than the object). The object  must be:

(a) between pole and focus
(b) at focus
(c) at the centre of curvature
(d) at infinity

Q 33 | Page 190

Explain what is meant by a virtual, magnified image.

Q 33.1 | Page 241

Draw a ray diagram to show the formation of a virtual magnified image of an object by a convex lens. In your diagram, the position of object and image with respect to the principal focus should be shown clearly.

Q 33.2 | Page 241

Three convex lenses are available having focal lengths of 4 cm, 40 cm and 4 m respectively. Which one would you choose as a magnifying glass and why?

Q 33.3 | Page 241

The angle of incidence for of light passing through the centre of curvature of a concave mirror is:

(a) 45°
(b) 90°
(c) 0°
(d) 180°

Q 34 | Page 190

Explain why, a real image can be projected on a screen but a virtual image cannot.

Q 34.1 | Page 241

Name one simple optical instrument in which the above arrangement of convex lens is used.

Q 34.3 | Page 241

In the concave reflector of a torch, the bulb is placed:

(a) between the pole and focus of reflector
(b) at the focus of reflector
(c) between focus and centre of curvature of reflector
(d) at the centre of curvature of reflector

Q 35 | Page 191

A convex lens has a focal length of 10 cm. At which of the following position should an object be placed so that this convex lens may act as a magnifying glass?

(a) 15 cm
(b) 7 cm
(c) 20 cm
(d) 25 cm

Q 35 | Page 241

Which one of the following materials cannot be used to make a lens?

(a) Water
(b) Glass
(c) Plastic
(d) Clay

Q 36 | Page 241

The focal length of a small concave mirror is 2.5 cm. In order to use this concave mirror as a dentist's mirror, the distance of tooth from the mirror should be:

(a) 2.5 cm
(b) 1.5 cm
(c) 4.5 cm
(d) 3.5 cm

Q 36 | Page 191

A small bulb is placed at the focal point of a converging lens. When the bulb is switched on, the lens produces:

(a) a convergent beam of light
(b) a divergent beam of light
(c) a parallel beam of light
(d) a patch of coloured light

Q 37 | Page 241

An object is 100 mm in front of a concave mirror which produces an upright (erect image). The radius of curvature of the mirror is:

(a) less than 100 mm
(b) between 100 mm and 200 mm
(c) exactly 200 mm
(d) more than 200 mm

Q 37 | Page 191

An illuminated object is placed at a distance of 20 cm from a converging lens of focal length 15 cm. The image obtained on the screen is:

(a) upright and magnified
(b) inverted and magnified
(c) inverted and diminished
(d) upright and diminished

Q 38 | Page 241

A virtual, erect and magnified image of an object is to be produced with a concave mirror of focal length 12 cm. Which of the following object distance should be chosen for this purpose?

(i) 10 cm
(ii) 15 cm
(iii) 20 cm

Q 38 | Page 191

An object is placed f and 2f of a convex lens. Which of the following statements correctly describes its image?

(a) real, larger than the object
(b) erect, smaller than the object
(c) inverted, same size as object
(d) virtual, larger than the object

Q 39 | Page 241

A concave mirror has a focal length of 25 cm. At which of the following distance should a person hold his face from this concave mirror so that it may act as a shaving mirror?

(a) 45 cm
(b) 20 cm
(c) 25 cm
(d) 30 cm

Q 39 | Page 191

Which of the following can make a parallel beam of light from a bulb falls on it?

(a) concave mirror as well as concave lens
(b) convex mirror as well as concave lens
(c) concave mirror as well as convex lens
(d) concave mirror as well as convex lens

Q 40 | Page 241

An object is placed at the following distances from a concave mirror of focal length 15 cm, turn by turn:

(a) 35 cm
(b) 30 cm
(c) 20 cm
(d) 10 cm
Which position of the object will produce:

(i) a magnified real image?
(ii) a magnified virtual image?
(iii) a diminished real image?
(iv) an image of same size as the object?

Q 40 | Page 190

In order to obtain a real image twice the size of the object with a convex lens of focal length 15 cm, the object distance should be:

(a) more than 5 cm but less than 10 cm
(b) more than 10 cm but less than 15 cm
(c) more than 15 cm but less than 30 cm
(d) more than 30 cm but less than 60 cm

Q 41 | Page 241

A converging lens is used to produce an image of an object on a screen,object on a screen. What change is needed for the image to be formed nearer to the lens?

(a) increase the focal length of the lens
(b) insert a diverging lens between the lens and the screen
(c) increase the distance of the object from the lens
(d) move the object closer to the lens

Q 42 | Page 242

A convex lens of focal length 8 cm forms a real image of the same size as the object. The distance between object and its image will be:

(a) 8 cm
(b) 16 cm
(c) 24 cm
(d) 32 cm

Q 43 | Page 242

A virtual, erect and magnified image of an object is to be obtained with a convex lens. For this purpose,the object should be placed:

(a) between 2F and infinity
(b) between F and optical centre
(c) between F and 2F
(d) at F

Q 44 | Page 242

A burning candle whose flame is 1.5 cm tall is placed at a certain distance in front of a convex lens. An image of candle flame is received on a white screen kept behind the lens. The image of flame also measures 1.5 cm. If is the focal length of convex lens, the candle is placed:

(a) at f
(b) between f and 2f
(c) at 2f
(d) beyond 2f

Q 45 | Page 245

A lens of focal length 12 cm forms an erect image three times the size of the object. The distance between the object and image is:

(a) 8 cm
(b) 16 cm
(c) 24 cm
(d) 36 cm

Q 46 | Page 242

If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed 19 cm from the lens, the image formed is slightly larger than object. The approximate focal length of the lens is:

(a) 5 cm
(b) 10 cm
(c) 18 cm
(d) 20 cm

Q 47 | Page 242

An object is placed at the following distance from a convex lens of focal length 15 cm:

(a) 35 cm
(b) 30 cm
(c) 20 cm
(d) 10 cm
Which position of the object will produce:
(i) a magnified real image?
(ii) a magnified virtual image?
(iii) a diminished real image?
(iv) an image of same size as the object?

Q 48 | Page 242

When an object is placed at a distance of 36 cm from a convex lens, an image of the same size as the object is formed. What will be the nature of image formed when the object is placed at a distance of:

10 cm from the lens?

Q 49.1 | Page 242

When an object is placed at a distance of 36 cm from a convex lens, an image of the same size as the object is formed. What will be the nature of image formed when the object is placed at a distance of:

20 cm from the lens?

Q 49.2 | Page 242

Draw a diagram to show how a converging lens focusses parallel rays of light?

Q 50.1 | Page 242

How would you alter the above diagram to show how a converging lens can produce a beam of parallel rays of light.

Q 50.2 | Page 242

#### Pages 0 - 290

As light rays pass from air into a glass prism, are they refracted towards or away from the normal?

Write the formula for a lens connecting image distance (v), object distance (u) and the focal length (f). How does the lens formula differ from the mirror formula?

According to the "New Cartesian Singh Convention" for mirrors, what sign has been given to the focal length of:

a concave mirror?

According to the "New Cartesian Singh Convention" for mirrors, what sign has been given to the focal length of:

a convex mirror?

Write down the magnification formula for a lens in terms of object distance and image distance. How does this magnification formula for a lens differ from the corresponding formula for a mirror?

As light rays emerge from a glass prism into air, are they refracted towards or away from the normal?

Which type of mirror has:

negative focal length?

What is the nature of a mirror having a focal length of, +10 cm?

Name a natural phenomenon which is caused by the dispersion of sunlight in the sky.

What is the nature of the image formed by a convex lens if the magnification produced by the lens is +3?

What is the nature of the image formed by a convex lens if the magnification produced by the lens is, – 0.5?

What information do we get about sunlight from the formation of a rainbow?

What kind of mirror can have a focal length of, −20 cm?

What is the position of image when an object is placed at a distance of 10 cm from a convex lens of focal length 10 cm?

Complete the following sentence:

All the distances are measured from the .......... of a spherical mirror.

What did Newton demonstrate by his experiments with the prism?

What colours make up white light?

Describe the nature of image formed when an object is placed at a distance of 30 cm from a convex lens of focal length 15 cm.

What sign (+ve or −ve) has been given to the following on the basis of Cartesian Sigh Convention?

Height of a real image.

What sign (+ve or −ve) has been given to the following on the basis of Cartesian Sigh Convention?

Height of a virtual image.

Give the meaning of the term VIBGYOR. With which phenomenon is it connected?

Describe the New Cartesian Sigh Convention used in optics. Draw a labelled diagram to illustrate this sign convention.

At what distance from a converging lens of focal length 12 cm must an object be placed in order that an image of magnification 1 will be produced?

State and explain the New Cartesian Sign Convention for spherical lenses.

According to New Cartesian Sign Convention:

(a) focal length of concave mirror is positive and that of convex mirror is negative
(b) focal length of both concave and convex mirrors is positive
(c) focal length of both concave and convex mirrors is negative
(d) focal length of concave mirror is negative and that of convex mirror is positive

Giving reasons, state the 'signs' (positive or negative) which can be given to the following:

(a) object distance (u) for a concave mirror or convex mirror
(b) image distance (v) for a concave mirror
(c) image distance (v) for a convex mirror

In the formation of spectrum of white light by a prism:

which colour is deviated least?

In the formation of spectrum of white light by a prism:

which colour is deviated most?

An object 4 cm high is placed at a distance of 10 cm from a convex lens of focal length 20 cm. Find the position, nature and size of the image.

What colours lie on the two sides of the 'green colour' in the spectrum of white light?

According to New Cartesian Sign Convention:

(a) focal length of concave mirror is positive and that of convex mirror is negative
(b) focal length of both concave and convex mirrors is positive
(c) focal length of both concave and convex mirrors is negative
(d) focal length of concave mirror is negative and that of convex mirror is positive

Name the scientist who discovered that sunlight consists of seven colours.

A small object is so placed in front of a convex lens of 5 cm focal length that a virtual image is formed at a distance of 25 cm. Find the magnification.

One of the following does not apply to a concave mirror this is:
(a) focal length is negative
(b) image distance can be positive or negative
(c) image distance is always positive
(d) height of image can be positive or negative

Find the position and nature of the image of an object 5 cm high and 10 cm in front of a convex lens of focal length 6 cm.

What is the order of colours in a rainbow, from the outside to the inside?

Calculate the focal length of a convex lens which produces a virtual image at a distance of 50 cm of an object placed 20 cm in front of it.

Which colour of the spectrum has

longest wavelength,

Which colour of the spectrum has

shortest wavelength?

Which light has the longer wavelength : red light or blue light?

An object is placed at a distance of 100 cm from a converging lens of focal length 40 cm.
(i) What is the nature of image?
(ii) What is the position of image?

Which colour of light has the shorter wavelength − red or violet?

A convex lens produces an inverted image magnified three times of an object placed at a distance of 15 cm from it. Calculate focal length of the lens.

A converging lens of focal length 5 cm is placed at a distance of 20 cm from a screen. How far from the lens should an object be placed so as to form its real image on the screen?

Fill in the blank with suitable word:

When a ray of light enters a prism, it bends ................ the normal ; as it leaves the prism, it bends ................. the normal.

An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.

At what distance should an object be placed from a convex lens of focal length 18 cm to obtain an image at 24 cm from it on the other side? What will be the magnification produced in this case?

What happens when a ray of ordinary light is passed through a triangular glass prism?

What will happen if another similar glass prism is placed upside down behind the first prism?

An object 2 cm tall is placed on the axis of a convex lens of focal length 5 cm at a distance of 10 m from the optical centre of the lens. Find the nature, position and size of the image formed. Which case of image formation by convex lenses is illustrated by this example?

When a beam of white light is passed through a prism, it splits to form lights of seven colours. Is it possible to recombine the lights of seven colours to obtain the white light again? Explain your answer.

The filament of a lamp is 80 cm from a screen and a converging lens forms an image of it on a screen, magnified three times. Find the distance of the lens from the filament and the focal length of the lens.

What is spectrum? What is the name of glass shape used to produce a spectrum?

How many colours are there in a full spectrum of white light? Write the various colours of spectrum in the order, starting with red.

What is meant by dispersion of white light? Describe the formation of rainbow in the sky with the help of a diagram.

An erect image 2.0 cm high is formed 12 cm from a lens, the object being 0.5 cm high. Find the focal length of the lens.

A convex lens of focal length 0.10 m is used to form a magnified image of an object of height 5 mm placed at a distance of 0.08 m from the lens. Calculate the position, nature and size of the image.

In the figure given alongside, a narrow beam of white light is shown to pass through a triangular glass prism. After passing through the prism, it produces a spectrum YX on the screen.

State the colour seen (i) at X, and (ii) at Y.

In the figure given alongside, a narrow beam of white light is shown to pass through a triangular glass prism. After passing through the prism, it produces a spectrum YX on the screen.

Why do different colours of white light bend through different angles with respect to the incident beam of light?

Draw a diagram to show how white light can be dispersed into a spectrum by using a glass prism. Mark the various colours of the spectrum.

A convex lens of focal length 6 cm is held 4 cm from a newspaper which has print 0.5 cm high. By calculation, determine the size and nature of the image produced.

Determine how far an object must be placed in front of a converging lens of focal length 10 cm in order to produce an erect (upright) image of linear magnification 4.

Make two diagrams to explain refraction and dispersion.

A lens of focal length 20 cm is used to produce a ten times magnified image of a film slide on a screen. How far must the slide be placed from the lens?

Describe how you could demonstrate that white light is composed of a number of colours.

An object placed 4 cm in front of a converging lens produces a real image 12 cm from the lens.
(a) What is the magnification of the image?
(b) What is the focal length of the lens?
(c) Draw a ray diagram to show the formation of image. Mark clearly F and 2F in the diagram.

How could you show that the colours of the spectrum combine to give white light?

Which is refracted most by a prism : red light or violet light? Explain why?

An object 2 cm tall stands on the principal axis of a converging lens of focal length 8 cm. Find the position, nature and size of the image formed if the object is:
(i) 12 cm from the lens
(ii) 6 cm from the lens
State one practical application each of the use of such a lens with the object in position (i) and (ii).

An object 3 cm high is placed 24 cm away from a convex lens of focal length 8 cm. Find by calculations, the position, height and nature of the image.

Draw a diagram to show the refraction of light through a glass prism. On this diagram, mark
(i) incident ray
(ii) emergent ray, and
(iii) angle of deviation.

If the object is moved to a point only 3 cm away from the lens, what is the new position, height and nature of the image?

What is a rainbow? What are the two conditions necessary for the formation of a rainbow in the sky?

Which of the above two cases illustrates the working of a magnifying glass?

What acts as tiny prisms in the formation of a rainbow?

Name the process which is involved in the formation of a rainbow.

What are the seven colours seen in a rainbow?

A beam of white light is shone onto a glass prism. The light cannot be:
(a) deviated
(b) dispersed
(c) focused
(d) refracted

Find the nature, position and magnification of the images formed by a convex lens of focal length 0.20 m if the object is placed at a distance of:

0.50 m

Find the nature, position and magnification of the images formed by a convex lens of focal length 0.20 m if the object is placed at a distance of:

0.25 m

Find the nature, position and magnification of the images formed by a convex lens of focal length 0.20 m if the object is placed at a distance of:

0.15 m

A beam of white light falls on a glass prism. The colour of light which undergoes the least bending on passing through the glass prism is:
(a) violet
(b) red
(c) green
(d) blue

A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be
(a) both concave
(b) both convex
(c) the mirror is concave and the lens is convex
(d) the mirror is convex, but the lens is concave

The colour of white light which suffers the maximum bending (or maximum refraction) on passing through a glass prism is:
(a) yellow
(b) orange
(c) red
(d) violet

Linear magnification produced by a convex lens can be:
(a) less than 1 or more than 1
(b) less than 1 or equal to 1
(c) more than 1 or equal to 1
(d) less than 1, equal to 1 or more than 1

Which of the following colour of white light is least deviated by the prism?
(a) green
(b) violet
(c) indigo
(d) yellow

Magnification produced by a concave lens is always:
(a) more than 1
(b) equal to 1
(c) less than 1
(d) more than 1 or less than 1

In order to obtain a magnification of, –3 (minus 3) with a convex lens, the object should be placed:
(a) between optical centre and F
(b) between F and 2F
(c) at 2F
(d) beyond 2F

The colour of white light which is deviated the maximum on passing through the glass prism is:
(a) blue
(b) indigo
(c) red
(d) orange

The splitting up of white light into seven colours on passing through a glass prism is called:
(a) refraction
(b) deflection
(c) dispersion
(d) scattering

A convex lens produces a magnification of + 5. The object is placed:
(a) at focus
(b) between f and 2f
(c) at less than f
(d) beyond 2

Which of the following coloured light has the least speed in glass prism?
(a) violet
(b) yellow
(c) red
(d) green

If a magnification of, –1 (minus 1) is obtained by using a converging lens, then the object has to be placed:
(a) within f
(b) at 2f
(c) beyond 2f
(d) at infinity

To obtain a magnification of, –0.5  with a convex lens, the object should be placed:
(a) at F
(b) between optical centre and F
(c) between F and 2F
(d) beyond 2F

The coloured light having the maximum speed in glass prism is:
(a) blue
(b) green
(c) violet
(d) yellow

An object is 0.09 m from a magnifying lens and the image is formed 36 cm from the lens. The magnification produced is:
(a) 0.4
(b) 1.4
(c) 4.0
(d) 4.5

Which of the following colour of white light has the least wavelength?
(a) red
(b) orange
(c) violet
(d) blue

To obtain a magnification of, –2 with a convex lens of focal length 10 cm, the object should be placed:
(a) between 5 cm and 10 cm
(b) between 10 cm and 20 cm
(c) at 20 cm
(d) beyond 20 cm

Out of the following, the colour of light having the maximum wavelength is:
(a) violet
(b) indigo
(c) green
(d) orange

A convex lens of focal length 15 cm produces a magnification of +4. The object is placed:
(a) at a distance of 15 cm
(b) between 15 cm and 30 cm
(c) at less than 15 cm
(d) beyond 30 cm

Why do you not see a spectrum of colours when light passes through a flat pane of glass?

If a magnification of, –1 is to be obtained by using a converging lens of focal length 12 cm, then the object must be placed:
(a) within 12 cm
(b) at 24 cm
(c) at 6 cm
(d) beyond 24 cm

Name some everyday objects:

which reflect all the colours in sunlight

Name some everyday objects:

which absorb all the colours in sunlight

Where in nature can you find evidence that white sunlight may be made of different colours?

In order to obtain a magnification of, –0.75 with a convex lens of focal length 8 cm, the object should be placed:
(a) at less than 8 cm
(b) between 8 cm and 16 cm
(c) beyond 16 cm
(d) at 16 cma

How is the reflection of light ray from a plane mirror different from the refraction of light ray as it enters a block of glass?

A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.

Rewrite the image distances in the correct order.

A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.

What would be the image distance if the object distance was 90 cm?

A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.

Which of the object distances gives the biggest image?

A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.

What is the focal length of this lens?

A magnifying lens has a focal length of 100 mm. An object whose size is 16 mm is placed at some distance from the lens so that an image is formed at a distance of 25 cm in front of the lens.

What is the distance between the object and the lens?

A magnifying lens has a focal length of 100 mm. An object whose size is 16 mm is placed at some distance from the lens so that an image is formed at a distance of 25 cm in front of the lens.

Where should the object be placed if the image is to form at infinity?

A lens forms a real image 3 cm high of an object 1 cm high. If the separation of object and image is 15 cm, find the focal length of the lens.

An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.

#### Pages 198 - 293

The phenomenon that causes the twinkling of stars is refraction of light.

Q 1 | Page 292

If the magnification of a body of size 1 m is 2, what is the size of the image?

Q 1 | Page 198

If the image formed by a lens is always diminished and erect, what is the nature of the lens?

Q 1 | Page 251

What type of image/images are formed by:

a concave mirror?

Q 1.2 | Page 205

A 50 cm tall object is at a very large distance from a diverging lens. A virtual, erect and diminished image of the object is formed at a distance of 20 cm in front of the lens. How much is the focal length of the lens?

Q 2 | Page 255

Name two effects produced by the atmospheric refraction.

Q 2 | Page 292

What is the position of the image when an object is placed at a distance of 20 cm from a concave mirror of focal length 20 cm?

Q 2 | Page 198

Copy and complete the diagram below to show what happens to the rays of light when they pass through the concave lens:

Q 2 | Page 251

What is the nature of image formed by a concave mirror if the magnification produced by the mirror

+4

Q 3.1 | Page 198

Which phenomenon makes us see the sun:

a few minutes before actual sunrise?

Q 3.1 | Page 292

Which type of lenses are:

thinner in the middle than at the edges?

Q 3.1 | Page 252

Which phenomenon makes us see the sun:

a few minutes after actual sunset?

Q 3.2 | Page 292

What is the nature of image formed by a concave mirror if the magnification produced by the mirror

−2?

Q 3.2 | Page 198

Which type of lenses are:

thicker in the middle than at the edges?

Q 3.2 | Page 252

A ray of light is going towards the focus of a concave lens. draw a ray diagram to show the path of this ray of light after refraction through the lens.

Q 4 | Page 252

State the relation between object distance, image distance and focal length of a spherical mirror (concave mirror or convex mirror).

Q 4 | Page 198

Atmospheric refraction causes advance sunrise and delayed sunset. By how much time is:

Q 4.1 | Page 292

Atmospheric refraction causes advance sunrise and delayed sunset. By how much time is:

sunset delayed?

Q 4.2 | Page 292

State whether the following statement is true or false:
The planets twinkle at night due to atmospheric refraction of light.

Q 5 | Page 292

Write the mirror formula. Give the meaning of each symbol which occurs in it.

Q 5 | Page 198

What type of images can a convex lens make?

Q 5.1 | Page 252

What type of image is always made by a concave lens?

Q 5.2 | Page 252

Name the phenomenon due to which the stars seem higher in the sky than they actually are.

Q 6 | Page 292

Take down this figure into your answer book and complete the path of the ray.

Q 6 | Page 252

What is the ratio of the height of an image to the height of an object known as?

Q 6 | Page 198

Define linear magnification produced by a mirror.

Q 7 | Page 198

Fill in the following blank with suitable word:
We can see the sun about ................ minutes before the actual sunrise and about ................ minutes after the actual sunset because of atmospheric ................

Q 7 | Page 292

Fill in the following blank with suitable word:

A convex lens .................. rays of light, whereas a concave lens .................. rays of light.

Q 7.1 | Page 252

Fill in the following blank with suitable word:

Lenses refract light to form images: a..................... lens can form both real and virtual images, but a diverging lens forms only ...................... images.

Q 7.2 | Page 252

Why do stars seem higher than they actually are? Illustrate your answer with the help of a diagram.

Q 8 | Page 292

Things always look small on viewing through a lens. What is the nature of the lens?

Q 8 | Page 252

Write down a formula for the magnification produced by a concave mirror.

in terms of height of object and height of image

Q 8.1 | Page 198

Write down a formula for the magnification produced by a concave mirror.

in terms of object distance and image distance

Q 8.2 | Page 198

Explain why, the sun can be seen about two minutes before actual sunrise. Draw a diagram to Illustrate your answer.

Q 9 | Page 292

An object lies at a distance of 2f from a concave lens of focal length f. Draw a ray-diagram to illustrate the image formation.

Q 9 | Page 252

Explain why, if we look at objects through the hot air over a fire, the objects appear to be moving (or shaking) slightly.

Q 10 | Page 292

Describe the nature of image formed when the object is placed at a distance of 20 cm from a concave mirror of focal length 10 cm

Q 10 | Page 198

Show by drawing a ray-diagram that the image of an object formed by a concave lens is virtual, erect and diminished.

Q 10 | Page 252

Fill in the following blank with suitable word:

If the magnification has a plus sign, than image is ......... and.........

Q 10.1 | Page 198

Fill in the following blank with suitable word:

If the magnification has a minus sign, than the image is ......... and .......

Q 10.2 | Page 198

Give the position, size and nature of image of formed by a concave lens when the object is placed:
anywhere between optical centre and infinity.

Q 11.1 | Page 252

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm.

Q 11.1 | Page 198

What is atmospheric refraction? What causes atmospheric refraction?

Q 11.1 | Page 292

Why do stars twinkle on a clear night?

Q 11.2 | Page 292

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm.

Calculate the image distance.

Q 11.2 | Page 198

Give the position, size and nature of image of formed by a concave lens when the object is placed:

at infinity.

Q 11.2 | Page 252

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm.

State two characteristics of the image formed.

Q 11.3 | Page 198

Explain why, the planets do not twinkle at night.

Q 11.3 | Page 292

The twinkling of stars is due to atmospheric:
(a) reflection of light
(b) dispersion of light
(c) interference of light
(d) refraction of light

Q 12 | Page 292

If an object of 10 cm height is placed at a distance of 36 cm from a concave mirror of focal length 12 cm, find the position, nature and height of the image.

Q 12 | Page 198

Which type of lens is :

a converging lens, and which is

Q 12.1 | Page 252

Which type of lens is

Q 12.2 | Page 252

At what distance from a concave mirror focal length 10 cm should an object 2 cm long be placed in order to get an erect image 6 cm tall?

Q 13 | Page 198

The atmospheric refraction of light causes the twinkling of:
(a) planets only
(b) stars only
(c) planets and stars
(d) stars and satellites

Q 13 | Page 293

With the help of a diagram, explain why the image of an object viewed through a concave lens appears smaller and closer than the object.

Q 13 | Page 252

The stars appear higher in the sky than they actually are, due to:
(a) diffraction of light
(b) scattering of light
(c) refraction of light
(d) reflection of light

Q 14 | Page 293

When an object is placed at a distance of 15 cm from a concave mirror, its image is formed at 10 cm in front of the mirror. Calculate the focal length of the mirror.

Q 14 | Page 198

How would a pencil look like if you saw it through

a concave lens  Is the image real or virtual?

Q 14.1 | Page 252

How would a pencil look like if you saw it through How would a pencil look like if you saw it through

Q 14.2 | Page 252

An object 3 cm high is placed at a distance of 8 cm from a concave mirror which produces a virtual image 4.5 cm high:

(i) What is the focal length of the mirror?
(ii) What is the position of image?
(iii) Draw a ray-diagram to show the formation of image.

Q 15 | Page 198

The stars twinkle but the planets do not twinkle at night because:
(a) the stars are small but the planets are large
(b) the stars are very large but planets are small
(c) the stars are much nearer but planets are far off
(d) the stars are far off but planets are nearer to earth

Q 15 | Page 293

An object is placed 10 cm from a lens of focal length 5 cm. Draw the ray diagrams to show the formation of image if the lens is  converging,

Q 15.1 | Page 252

An object is placed 10 cm from a lens of focal length 5 cm. Draw the ray diagrams to show the formation of image if the lens is  diverging.

Q 15.2 | Page 252

State one practical use each of convex mirror, concave mirror, convex lens and concave lens.

Q 15.3 | Page 252

As light from a far off star comes down towards the earth:
(a) it bends away from the normal
(b) it bends towards the normal
(c) it does not bend at all
(d) it is reflected back

Q 16 | Page 293

A converging mirror forms a real image of height 4 cm of an object of height 1 cm placed 20 cm away from the mirror:

(i) Calculate the image distance.
(ii) What is the focal length of the mirror?

Q 16 | Page 198

Construct ray diagrams to illustrate the formation of a virtual image using  a converging lens,

Q 16.1 | Page 252

Construct ray diagrams to illustrate the formation of a virtual image using   a diverging lens.

Q 16.2 | Page 252

What is the difference between the two images formed above?

Q 16.3 | Page 252

A diverging lens is used in:
(a) a magnifying glass
(b) a car to see objects on rear side
(c) spectacles for the correction of short sight
(d) a simple camera

Q 17 | Page 252

An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed so that a sharp focussed image can be obtained? Find the size and nature of image.

Q 17 | Page 198

We can see the sun before the actual sunrise by about:
(a) 5 minutes
(b) 2 minutes
(c) 2 hours
(d) 20 minutes

Q 17 | Page 293

When an object is kept at any distance in front of a concave lens, the image formed is always:
(a) virtual, erect and magnified
(b) virtual, inverted and diminished.
(c) virtual, erect and diminished
(d) virtual, erect and same size as object

Q 18 | Page 252

An object 3 cm high is placed at a distance of 10 cm in front of a converging mirror of focal length 20 cm. Find the position, nature and size of the image formed.

Q 18 | Page 199

Due to atmospheric refraction of sunlight, the time from sunrise to sunset is lengthened by about:
(a) 6 minutes
(b) 2 minutes
(c) 4 minutes
(d) 5 minutes

Q 18 | Page 293

When sunlight is concentrated on a piece of paper by a spherical mirror or lens, then a hole can be burnt in it. For doing this, the paper must be placed at he focus of:
(a) either a convex mirror or convex lens
(b) either a concave mirror or concave lens
(c) either a concave mirror or convex lens
(d) either a convex mirror or concave lens

Q 19 | Page 252

The day is longer on the earth by about 4 minutes because:
(a) the earth is round in shape
(b) the earth rotates on its axis
(c) the earth revolves around the sun
(d) the earth has atmosphere

Q 19 | Page 293

A concave mirror has a focal length of 4 cm and an object 2 cm tall is placed 9 cm away from it. Find the nature, position and size of the image formed.

Q 19 | Page 199

A beam of parallel light rays is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the diagram below:

Which of the following could be inside the box?
(a) a rectangular glass block
(b) a concave lens
(c) a convex lens
(d) a glass prism

Q 20 | Page 253

When an object is placed 20 cm from a concave mirror, a real image magnified three times is formed. Find:

(a) the focal length of the mirror.
(b) Where must the object be placed to give a virtual images three times the height of the object?

Q 20 | Page 199

We know that light refracts (or bends) when it goes from one medium to another. Now, the atmosphere contains only air. Then how does light get refracted on passing through only air in the atmosphere?

Q 20 | Page 293

By how much time the day would have been shorter if the earth had no atmosphere?

Q 21 | Page 293

A beam of light is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the following figure:

The box contains:
(a) a glass prism
(b) a concave lens
(c) a convex lens
(d) a parallel-sided glass slab

Q 21 | Page 253

A dentist's mirror has a radius of curvature of 3 cm. How far must it be placed from a small dental cavity to give a virtual image of the cavity that is magnified five times?

Q 21 | Page 199

Which of the following can form a virtual image which is always smaller than the object?
(a) a plane mirror
(b) a convex lens
(c) a concave lens
(d) a concave mirror

Q 22 | Page 253

A large concave mirror has a radius of curvature of 1.5 m. A person stands 10 m in front of the mirror. Where is the person's image?

Q 22 | Page 199

A student claims that because of atmospheric refraction, the sun can be seen after it has set, and the day is, therefore, longer than if the earth had no atmosphere.

What does the student mean by saying that the sun can be seen after it has set?

Q 22.1 | Page 293

A student claims that because of atmospheric refraction, the sun can be seen after it has set, and the day is, therefore, longer than if the earth had no atmosphere.

Do you think that the students conclusion is correct?

Q 22.2 | Page 293

When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object.

What is the nature of lens A?

Q 23 | Page 253

An object of 5.0 cm size is placed at a distance of 20.0 cm from a converging mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed to get the sharp image? Also calculate the size of the image.

Q 23 | Page 199

When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object.

What is the focal length of lens A?

Q 23.1 | Page 253

When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object.

What is the focal length of lens B?

Q 23.2 | Page 253

When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object.

What is the nature of lens B?

Q 23.4 | Page 253

When a fork is seen through lenses A and B one by one, it appears as shown in the diagrams. What is the nature of (i) lens A, and (ii) lens B? Give reason for your answer.

Q 24 | Page 253

A concave mirror produces three times enlarged virtual image of an object placed at 10 cm in front of it. Calculate the radius of curvature of the mirror.

Q 24 | Page 199

A bright object 50 mm high stands on the axis of a concave mirror of focal length 100 mm and at a distance of 300 mm from the concave mirror. How big will the image be?

Q 25 | Page 199

What kind of lens can form:

an inverted magnified image?

Q 25.1 | Page 253

What kind of lens can form:

an erect magnified image?

Q 25.2 | Page 253

What kind of lens can form:

an inverted diminished image?

Q 25.3 | Page 253

What kind of lens can form:

am erect diminished image?

Q 25.4 | Page 253

How far should an object be placed from the pole of a converging mirror of focal length 20cm to form a real image of the size exactly 1/4th the size of the object?

Q 26 | Page 199

When an object is placed at a distance of 50 cm from a concave spherical mirror, the magnification produced is, -1/2. Where should the object be placed to get a magnification of, -1/5?

Q 27 | Page 199

An object is placed (a) 20 cm, (b) 4 cm, in front of a concave mirror of focal length 12 cm. Find the nature and position of the image formed in each case.

Q 28 | Page 199

A concave mirror produces a real image 1 cm tall of an object 2.5 mm tall placed 5 cm from the mirror. Find the position of the image and the focal length of the mirror.

Q 29 | Page 199

A man holds a spherical shaving mirror of radius of curvature 60 cm, and focal length 30 cm, at a distance of 15 cm, from his nose. Find the position of image, and calculate the magnification.

Q 30 | Page 199

An object is placed just outside the principal focus of concave mirror. Draw a ray diagram to show how the image is formed, and describe its size, position and nature.

Q 31.1 | Page 199

If the object is moved further away from the mirror, what changes are there in the position and size of the image?

Q 31.2 | Page 199

An object is 24 cm away from a concave mirror and its image is 16 cm from the mirror. Find the focal length and radius of curvature of the mirror, and the magnification of the image.

Q 32 | Page 199

Linear magnification produced by a concave mirror may be:

(a) less than 1 or equal to 1
(b) more than 1 or equal than 1
(c) less than 1, more than 1 or equal to 1
(d) less than 1 or more than 1

Q 33 | Page 199

Magnification produced by a convex mirror is always:

(a) more than 1
(b) less than 1
(c) equal to 1
(d) more or less than 1

Q 34 | Page 199

In order to obtain a magnification of −2 (minus 2) with a concave mirror, the object should be placed:

(a) between pole and focus
(b) between focus and centre of curvature
(c) at the centre of curvature
(d) beyond the centre of curvature

Q 35 | Page 199

A concave mirror produces magnification of +4. The object is placed:

(a) at the focus
(b) between focus and centre of curvature
(c) between focus and pole
(d) between the centre of curvature

Q 36 | Page 199

If a magnification of, −1 (minus one) is to be obtained by using a converging mirror, then the object has to be placed:

(a) between pole and focus
(b) at the centre of curvature
(c) beyond the centre of curvature
(d) at infinity

Q 37 | Page 199

In order to obtain a magnification of, −0.6 (minus 0.6) with a concave mirror, the object must be placed:

(a) at the focus
(b) between pole and focus
(c) between focus and centre of curvature
(d) beyond the centre of curvature

Q 38 | Page 199

An object is placed at a large distance in front of a concave mirror of radius of curvature 40 cm. The image will be formed in front of the mirror at a distance:

(a) 20 cm
(b) 30 cm
(c) 40 cm
(d) 50 cm

Q 39 | Page 200

In order to obtain a magnification of, −1.5 with a concave mirror of focal length 16 cm, the object will have to be placed at a distance

(a) between 6 cm and 16 cm
(b) between 32 cm and 16 cm
(c) between 48 cm and 32 cm
(d) beyond 64 cm

Q 40 | Page 199

Linear magnification (m) produced by a rear view mirror fitted in vehicles:

(a) is equal to one
(b) is less than one
(c) is more than one
(d) can be more less than one depending on the position of object

Q 41 | Page 200

Between which two points of concave mirror should an object be placed to obtain a magnification of:

(a) −3
(b) +25
(c) −0.4

Q 42 | Page 200

At what distance from a concave mirror of focal length 10 cm should an object be placed so that:

its real image is formed 20 cm from the mirror?

Q 43.1 | Page 200

At what distance from a concave mirror of focal length 10 cm should an object be placed so that:

its virtual image is formed 20 cm from the mirror?

Q 43.2 | Page 200

If a concave mirror has a focal length of 10 cm, find the two positions where an object can be placed to give, in each case, an image twice the height of the object.

Q 44 | Page 200

A mirror forms an image which is 30 cm from an object and twice its height.

(a) Where must the mirror be situated?
(b) What is the radius of curvature?
(c) Is the mirror convex or concave?

Q 45 | Page 200

#### Pages 205 - 298

What is the colour of the sunlight:

scattered by the dust particles in the atmosphere?

Q 1.1 | Page 297

The lens A produces a magnification of, − 0.6 whereas lens B produces a magnification of + 0.6.

What is the nature of lens A?

Q 1.1 | Page 255

What type of image/images are formed by:

a convex mirror?

Q 1.1 | Page 205

The lens A produces a magnification of, − 0.6 whereas lens B produces a magnification of + 0.6.

What is the nature of lens B

Q 1.2 | Page 255

What is the colour of the sunlight

scattered by the air molecules in the atmosphere?

Q 1.2 | Page 297

Which of the two is scattered more easily : light of shorter wavelengths or light of longer wavelengths?

Q 2 | Page 297

Which mirror has a wider field of view?

Q 2 | Page 205

An object is placed at a distance of 4 cm from a concave lens of focal length 12 cm. Fine the position and nature of the image.

Q 3 | Page 256

If you want to see an enlarged image of your face, state whether you will use a concave mirror or a convex mirror?

Q 3 | Page 205

State whether the following statements are true or false:

The scattering away of red light makes the sky appear blue during the day time.

Q 3.1 | Page 297

State whether the following statements are true or false:

The scattering away of blue light makes the sun appear red at sunset.

Q 3.2 | Page 297

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray-diagram.

Q 4 | Page 256

Which mirror always produces a virtual, erect and diminished image of an object?

Q 4 | Page 205

What colour does the sky appear to an astronaut?

Q 4 | Page 297

An object is placed at a long distance in front of a convex mirror of radius of curvature 30 cm. State the position of its image.

Q 5 | Page 205

Which effect is illustrated by the observation that when a beam of sunlight enters a dusty room, then its path becomes visible to us.

Q 5 | Page 297

An object 60 cm from a lens gives a virtual image at a distance of 20 cm in front of the lens. What is the focal length of the lens? Is the lens converging or diverging? Give reasons for your answer.

Q 5 | Page 256

A concave lens of 20 cm focal length forms an image 15 cm from the lens. Compute the object distance.

Q 6 | Page 256

Name the spherical mirror which can produce a real and diminished image of an object.

Q 6 | Page 205

State two effects produced by the scattering of light by the atmosphere.

Q 6 | Page 297

Name the spherical mirror which can produce a virtual and diminished image of an object.

Q 7 | Page 205

What is tyndall effect? Explain with an example.

Q 7 | Page 297

A concave lens has focal length 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also find the magnification produced by the lens.

Q 7 | Page 256

One wants to see a magnified image of an object in a mirror. What type of mirror should one use?

Q 8 | Page 205

Calculate the image distance for an object of height 12 mm at a distance of 0.20 m from a concave lens of focal length 0.30 m, and state the nature and size of the image.

Q 8 | Page 256

What happens when a beam of sunlight enters a dusty room through a window? Explain your answer.

Q 8 | Page 297

Why does the sky appear blue on a clear day?

Q 9 | Page 298

Name the mirror which can give:

an erect and diminished image of an object.

Q 9.1 | Page 205

Name the mirror which can give:

an erect and enlarged image of an object.

Q 9.2 | Page 205

An object is placed 20 cm from (a) a converging lens, and (b) a diverging lens, of focal length 15 cm. Calculate the image position and magnification in each case.

Q 10 | Page 256

State whether the following statement is true or false:
A diverging mirror is used as a rear-view mirror.

Q 10 | Page 205

Why does the sky appear dark (or black) to an astronaut instead of blue?

Q 10 | Page 298

A 2.0 cm tall object is placed 40 cm from a diverging lens of focal length 15 cm. Find the position and size of the image.

Q 11 | Page 256

Why does sun appear red at sunrise and sunset?

Q 11 | Page 298

What type of mirror should be used:

as a shaving mirror?

Q 11.1 | Page 205

What type of mirror should be used:

as a shaving mirror?

Q 11.2 | Page 205

Why does the sun appear red at sunset?

Q 12 | Page 298

Which type or mirror is usually used as a rear-view mirror in motor cars?

Q 12 | Page 205

(a) Find the position and size of the virtual image formed when an object 2 cm tall is placed 20 cm from:
(i) a diverging lens of focal length 40 cm.
(ii) a converging lens of focal length 40 cm.
(b) Draw labelled ray diagrams to show the formation of images in case (i) and (ii) above (The diagrams may not be according to scale).

Q 12 | Page 256

What kind of mirrors are used in big shopping centres to watch the activities of the customers?

Q 13 | Page 205

Why are the 'danger signal' lights red in colour?

Q 13 | Page 298

A small object is placed 150 mm away from a diverging lens of focal length 100 mm.
(i) Copy the figure below and draw rays to show how an image is formed by the lens.
Figure
(ii) Calculate the distance of the image from the lens by using the lens formula.

Q 13.1 | Page 256

The diverging lens in part (a) is replaced by a converging lens also of focal length 100 mm. The object remains in the same position and an image is formed by the converging lens. Compare two properties of this image with those of the image formed by the diverging lens in part (a).

Q 13.2 | Page 256

A ray of light of going towards the focus of a convex mirror becomes parallel to the principal axis after reflection from the mirror. Draw a labelled diagram to represent this situation.

Q 14 | Page 205

A concave lens produces an image 20 cm from the lens of an object placed 30 cm from the lens. The focal length of the lens is:
(a) 50 cm
(b) 40 cm
(c) 60 cm
(d) 30 cm

Q 14 | Page 256

Draw a neat and labelled diagram of the experimental set up for observing the scattering of light in a colloidal solution of sulphur to show how the sky appears blue, and the sun appears red at sunrise and sunset.

Q 14.1 | Page 298

Out of blue light and red light, which one is scattered more easily?

Q 14.2 | Page 298

Which component of sunlight is scattered away when the sun appears red at sunrise or sunset?

Q 14.3 | Page 298

What causes the scattering of blue component of sunlight in the atmosphere?

Q 14.4 | Page 298

Fill in the following blank with a suitable word:
A ray of light which is parallel to the principal axis of a convex mirror, appears to be coming from ............ after reflection from the mirror.

Q 15 | Page 205

The blue colour of sky is due to:
(a) refraction of light
(b) dispersion of light
(c) diffraction of light
(d) scattering of light

Q 15 | Page 298

Only one of the following applies to a concave lens. This is:
(a) focal length is positive
(b) image distance can be positive or negative
(c) height of image can be positive or negative
(d) image distance is always negative

Q 15 | Page 256

The magnification produced by a spherical mirror and a spherical lens is + 0.8.
(a) The mirror and lens are both convex
(b) The mirror and lens are both concave
(c) The mirror is concave but the lens is convex
(d) The mirror is convex but the lens is concave

Q 16 | Page 256

Why do we prefer a convex mirror as a rear-view mirror in vehicles?

Q 16 | Page 205

The red colour of the sun at the time of sunrise and sunset is because:
(a) red colour is least scattered
(b) blue colour is least scattered
(c) red colour is most scattered
(d) blue colour is most scattered

Q 16 | Page 298

Which of the following is not caused by the atmospheric refraction of light?
(a) twinkling of stars at night
(b) sun appearing higher in the sky than it actually is
(c) sun becoming visible two minutes before actual sunrise
(d) sun appearing red at sunset

Q 17 | Page 298

Why can you not use a concave mirror as a rear-view mirror in vehicles?

Q 17 | Page 205

The magnification produced by a spherical lens and a spherical mirror is + 2.0.
(a) The lens and mirror are both concave
(b) The lens and mirror are both convex
(c) The lens is convex but the mirror is concave
(d) The lens is concave but the mirror is convex

Q 17 | Page 256

The sky appears blue because some of the blue component of sunlight is scattered by:
(a) gas molecules present in air
(b) dust particles present in air
(c) water droplets suspended in air
(d) soot particles present in air

Q 18 | Page 298

A camera fitted with a lens of focal length 50 mm is being used to photograph a flower that is 5 cm in diameter. The flower is placed 20 cm in front of the camera lens.

At what distance from the film should the lens be adjusted to obtain a sharp image of the flower?

Q 18.1 | Page 257

Where would the image be formed by a convex mirror if the object is placed:

between infinity and pole of the mirror?

Draw labelled ray-diagrams to show the formation of image in both the case.

Q 18.1 | Page 205

What would be the diameter of the image of the flower on the film?

Q 18.2 | Page 257

Where would the image be formed by a convex mirror if the object is placed:

at infinity?

Draw labelled ray-diagrams to show the formation of image in both the case.

Q 18.2 | Page 205

An object is 2 m from a lens which forms an erect image one-fourth (exactly) the size of the object. Determine the focal length of the lens. What type of lens is this?

Q 19 | Page 256

Sunset is red because at that time the light coming from the sun has to travel:
(a) lesser thickness of earth's atmosphere
(b) greater thickness of earth's atmosphere
(c) varying thickness of earth's atmosphere
(d) along the horizon

Q 19 | Page 298

The shiny outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror:

What will be the focal length of this mirror?

Q 19.1 | Page 206

The shiny outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror:

Which type of spherical mirror will it provide?

Q 19.2 | Page 206

The shiny outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror:

State whether this spherical mirror will diverge or converge light rays.

Q 19.3 | Page 206

What is the advantage of using a convex mirror as  rear-view mirror in vehicles as compared to a plane mirror? Illustrate your answer with the help of labelled diagrams.

Q 20 | Page 206

An image formed on a screen is three times the size of the object. The object and screen are 80 cm apart when the image is sharply focussed.

State which type of lens is used.

Q 20.1 | Page 257

In an experiment to study the scattering of light by passing a beam of white light through a colloidal solution of sulphur in a transparent glass tank:

Which colour is observed from the front of the glass tank? Does this colour correspond to the colour of sky on a clear day or the colour of sky around the sun at sunset?

Q 20.1 | Page 298

In an experiment to study the scattering of light by passing a beam of white light through a colloidal solution of sulphur in a transparent glass tank:

Which colour is observed from the sides of the glass tank? Does this colour correspond to the colour of sky on a clear day or the colour of sky around the sun at sunset?

Q 20.2 | Page 298

An image formed on a screen is three times the size of the object. The object and screen are 80 cm apart when the image is sharply focussed.

Calculate focal length of the lens.

Q 20.2 | Page 257

Explain why, when the sun is overhead at noon, it appears white, but when the same sun is near the horizon at sunset, it appears red.

Q 21 | Page 298

Give two uses of a convex mirror. Explain why you would choose convex mirror for these uses.

Q 21 | Page 206

Complete the following statement:
When the sun is setting, the light from it has to travel a ................ thickness of the earth's atmosphere and only ................ wavelength ................ light is able to reach us. Sunset is therefore ................

Q 22 | Page 298

What would your image look like if you stood close to a large:

convex mirror?

Q 22.1 | Page 206

What would your image look like if you stood close to a large:

concave mirror?

Q 22.2 | Page 206

Which of the following are concave mirrors and which convex mirrors?

Q 23.1 | Page 206

Shaving mirrors, Car headlight mirror, Searchlight mirror, Driving mirror, Dentist's inspection mirror, Touch mirror, Staircase mirror in a double-decker bus, Make-up mirror, Solar furnace mirror, Satellite TV dish, Shop security mirror.

Q 23.2 | Page 206

How will you distinguish between a plane mirror, a concave mirror and a convex mirror without touching them?

Q 24 | Page 206

If a driver has one convex and one plane rear-view mirror, how would the images in each mirror appear different?

Q 25 | Page 206

Draw a labelled ray diagram to show the formation of image of an object by a convex mirror. Mark clearly the pole, focus and centre of curvature on the diagram.

Q 26.1 | Page 206

What happens to the image when the object is moved away from the mirror gradually?

Q 26.2 | Page 206

State three characteristics of the image formed by a convex mirror.

Q 26.3 | Page 206

Draw a labelled ray diagram to show the formation of image in a convex-mirror when the object is at infinity. Mark clearly the pole and focus of the mirror in the diagram.

Q 27.1 | Page 206

State three characteristics of the image formed by a convex mirror.

Q 27.2 | Page 206

Draw diagram to show how a convex mirror can be used to give a large field of view.

Q 27.3 | Page 206

The image formed by a spherical mirror is virtual. The mirror will be:

(a) concave
(b) convex
(c) either concave or convex
(d) metallic

Q 28 | Page 206

Whatever be the position of the object, the image formed by a mirror is virtual, erect and smaller than the object. The mirror then must be:

(a) plane
(b) concave
(c) convex
(d) either concave or convex

Q 29 | Page 206

The mirror used by a dentist to examine the teeth of a person is:
(d) any one of the above

(a) convex
(b) concave
(c) plane
(d) any one of the above

Q 30 | Page 206

If the image formed is always virtual, the mirror can be:

(a) concave or convex
(b) concave or plane
(c) convex or plane
(d) only convex

Q 31 | Page 206

A concave mirror cannot be used as:

(a) a magnifying mirror
(b) a torch reflector
(c) a dentist's mirror
(d) a real view mirror

Q 32 | Page 206

A boy is standing in front of and close to a special mirror. He finds the image of his head bigger than normal, the middle part of his body of the same size, and his legs smaller than normal. The special mirror is made up of three types of mirrors in the following order from top downwards:

(a) Convex, Plane, Concave
(b) Plane, Convex, Concave
(c) Concave, Plane, Convex
(d) Convex, Concave, Plane

Q 33 | Page 206

The mirror which can form a magnified image of an object is:

(a) convex mirror
(b) plane mirror
(c) concave mirror
(d) both convex and concave mirror

Q 34 | Page 207

A real image of an object is to be obtained. The mirror required for this purpose is:

(a) convex
(b) concave
(c) plane
(d) either convex or concave

Q 35 | Page 207

Consider two statements A and B given below:
A : real image is always inverted
B :  virtual image is always erect
Out of these two statements:

(a) only A is true
(b) only B is true
(c) both A and B are true
(d) none is true

Q 36 | Page 207

The diagrams show the appearance of a fork when placed in front of and close to two mirrors A and B, turn by turn.
Figure

(a) Which mirror is convex
(b) Which mirror is concave

Q 37 | Page 207

The diagram shows a dish antenna which is used to receive television signals from a satellite. The antenna (signal detector) is fixed in front of the curved dish.
Figure

(a) What is the purpose of the dish?
(b) Should it be concave or convex?
(c) Where should the antenna be positioned to receive the strongest possible signals?
(d) Explain what change you would expect in the signals if a larger dish was used.

Q 38 | Page 207

A man standing in front of a special mirror finds his image having a very small head, a fat body and legs of normal size. What is the shape of:

(a) top part of the mirror?
(b) middle part of the mirror?
(c) bottom part of the mirror?

Q 39 | Page 207

Two big mirrors A and B are fitted side by side on a wall. A man is standing at such a distance from the wall that he can see the erect image of his face in both the mirrors. When the man starts walking towards the mirrors, he find that the size of his face in mirror A goes on increasing but that in mirror B remains the same.

(a) mirror A is concave and mirror B is convex
(b) mirror A is plane and mirror B is concave
(c) mirror A is concave and mirror B is plane
(d) mirror A is convex and mirror B is concave

Q 40 | Page 207

#### Pages 0 - 263

An object is kept at a distance of 5 cm in front of a convex mirror of focal length 10 cm. Calculate the position and magnification of the image and state its nature.

The lens A has a focal length of 25 cm whereas another lens B has a focal length of 60 cm. Giving reason state, which lens has more power : A or B.

An object is placed at a distance of 10 cm from a convex mirror of focal length 5 cm.

(a) Draw a ray-diagram showing the formation image
(b) State two characteristics of the image formed
(c) Calculate the distance of the image from mirror.

Which causes more bending (or more refraction) of light rays passing through it : a convex lens of long focal length or a convex lens of short focal length?

Name the physical quantity whose unit is dioptre.

An object is placed at a distance of 6 cm from a convex mirror of focal length 12 cm. Find the position and nature of the image.

Define 1 dioptre of power of a lens.

An object placed 20 cm in front of a mirror is found to have an image 15 cm (a) in front of it, (b) behind the mirror. Find the focal length of the mirror and the kind of mirror in each case.

Which type of lens has (a) a positive power, and (b) a negative power?

An arrow 2.5 cm high is placed at a distance of 25 cm from a diverging mirror of focal length 20 cm. Find the nature, position and size of the image formed.

Which of the two has a greater power : a lens of short focal length or a lens of large focal length?

A convex mirror used as a rear-view mirror in a car has a radius of curvature of 3 m. If a bus is located at a distance of 5 m from this mirror, find the position of image. What is the nature of the image?

A diverging mirror of radius of curvature 40 cm forms an image which is half the height of the object. Find the object and image positions.

How is the power of a lens related to its focal length?

Which has more power : a thick convex lens or a thin convex lens, made of the same glass? Give reason for your choice.

The radius of curvature of a convex mirror used as a rear view mirror in a moving car is 12.0 m. A truck is coming from behind it at a distance of 3.54 m. Calculate (a) position, and (b) size of the image relative to the size of the truck. What will be the nature of the image?

The focal length of a convex lens is 25 cm. What is its power?

Draw a diagram to represent a convex mirror. On this diagram mark principal axis, principal focus F and the centre of C if the focal length of convex mirror is 3 cm.

An object 1 cm tall is placed 30 cm in front of a convex mirror of focal length 20 cm. Find the size and position of the image formed by the convex mirror.

What is the power of a convex lens of focal length 0.5 m?

A shop security mirror 5.0 m from certain items displayed in the shop produces on-tenth magnification.

What is the type of mirror?

A shop security mirror 5.0 m from certain items displayed in the shop produces on-tenth magnification.

What is the radius of curvature of the mirror?

A converging lens has focal length of 50 mm. What is the power of the lens?

An object is placed 15 cm from (a) a converging mirror, and (b) a diverging mirror, of radius of curvature 20 cm. Calculate the image position and magnification in each case.

What is the power of a convex lens lens whose focal length is 80 cm?

An object 20 cm from a spherical mirror gives rise to virtual image 15 cm behind the mirror. Determine the magnification of the image and the type of mirror used.

A diverging lens has focal length of 3 cm. Calculate the power.

The power of a lens is + 0.2 D. Calculate its focal length.

The power of a lens is, −2 D. What is its focal length?

What is the nature of a lens having a power of + 0.5 D?

What is the nature of a lens whose power is, −4 D?

The optician's prescription for a spectacle lens is marked +0.5 D. What is the :
(a) nature of spectacle lens?
(b) focal length of spectacle lens?

A doctor has prescribed a corrective lens of power, −1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

A lens has a focal length of, −10 cm. What is the power of the lens and what is its nature?

The focal length of a lens is +150 mm. What kind of lens is it and what is its power?

Fill in the following blank with suitable words :

The reciprocal of the focal length in metres gives you the..........of the lens, which is measured in..........

Fill in the following blank with suitable word :

For converging lenses, the power is..........while for diverging lenses, the power is.........

An object of height 4 cm is placed at a distance of 15 cm in front of a concave lens of power, −10 dioptres. Find the size of the image.

An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5D. Find (i) focal length of the lens, and (ii) size of the image.

A convex lens of power 5 D and a concave lens of power 7.5 D are placed in contact with each other. What is the :
(a) power of this combination of lenses?
(b) focal length of this combination of lenses?

A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact with one another.
(a) What is the power of this combination?
(b) What is the focal length of this combination?
(c) Is this combination converging or diverging?

The power of a combination of two lenses X and Y is 5 D. If the focal length of lens X be 15 cm :
(a) calculate the focal length of lens Y.
(b) state the nature of lens Y.

Two lenses A and B have focal lengths of +20 cm and, −10 cm, respectively.
(a) What is the nature of lens A and lens B?
(b) What is the power of lens A and lens B?
(c) What is the power of combination if lenses A and B are held close together?

What do you understand by the power of a lens? Name one factor on which the power of a lens depends.

What is the unit of power of a lens? Define the unit of power of a lens.

A combination of lenses for a camera contains two converging lenses of focal lengths 20 cm and 40 cm and a diverging lens of focal length 50 cm. Find the power and focal length of the combination.A optical instrument in which the above arrangement of convex lens is used is a convex lens used to burn paper by focusing sunlight.

Two lenses A and B have power of (i) +2D and (ii) −4D respectively. What is the nature and focal length of each lens?

An object is placed at a distance of 100 cm from each of the above lenses A and B. Calculate (i) image distance, and (ii) magnification, in each of the two cases.

The focal lengths of four convex lenses PQR and S are 20 cm, 15 cm, 5 cm and 10 cm, respectively. The lens having greatest power is :
(a) P
(b) Q
(c) R
(d) S

A converging lens has a focal length of 50 cm. The power of this lens is :
(a) +0.2D
(b) −2.0D
(c) +2.0D
(d) −0.2D

A diverging lens has a focal length of 0.10 m. The power of this lens will be :
(a) +10.0D
(b) +1.0D
(c) −1.0D
(d) −10.0D

The power of a lens is +2.0D. Its focal length should be :
(a) 100 cm
(b) 50 cm
(c) 25 cm
(d) 40 cm

If a spherical lens has a power of, −0.25 D, the focal length of this lens will be :
(a) −4 cm
(b) −400 mm
(c) −4 m
(d) −40 cm

If a spherical lens has a power of, −0.25 D, the focal length of this lens will be :
(a) −4 cm
(b) −400 mm
(c) −4 m
(d) −40 cm

The power of a concave lens is 10 D and that of a convex lens is 6 D. When these two lenses are placed in contact with each other, the power of their combination will be :
(a) +16 D
(b) +4 D
(c) −16 D
(d) −4 D

The power of a converging lens is 4.5 D and that of a diverging lens is 3 D. The power of this combination of lenses placed close together is :
(a) +1.5D
(b) +7.5D
(c) −7.5D
(d) −1.5D

A convex lens of focal length 10 cm is placed in contact with a concave lens of focal length 20 cm. The focal length of this combination of lenses will be:
(a) +10 cm
(b) +20 cm
(c) −10 cm
(d) −20 cm

The optical prescription for a pair of spectacles is :
Right eye : −3.50 D
Left eye : −4.00 D

Are these lenses thinner at the middle or at the edges?

The optical prescription for a pair of spectacles is :
Right eye : −3.50 D
Left eye : −4.00 D

Which lens has a greater focal length?

The optical prescription for a pair of spectacles is :
Right eye : −3.50 D
Left eye : −4.00 D

Which is the weaker eye?

A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads :
Left eye : +2.50 D
Right eye : +2.00 D

Which lens bends the light rays more strongly?

A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads :
Left eye : +2.50 D
Right eye : +2.00 D

State whether these spectacle lenses will converge light rays or diverge light rays.

#### Page 280

The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
(a) presbyopia
(b) accommodation
(c) near-sightedness
(d) far-sightedness

Q 35 | Page 280

#### Page 263

A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads :
Left eye : +2.50 D
Right eye : +2.00 D

State whether these lenses are thicker in the middle or at the edges.

Q 40.1 | Page 263

#### Extra questions

In order to obtain a magnification of, −1.5 with a concave mirror of focal length 16 cm, the object will have to be placed at a distance

(a) between 6 cm and 16 cm
(b) between 32 cm and 16 cm
(c) between 48 cm and 32 cm
(d) beyond 64 cm

An object 1 cm tall is placed 30 cm in front of a convex mirror of focal length 20 cm. Find the size and position of the image formed by the convex mirror.

The shiny outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror:

State whether this spherical mirror will diverge or converge light rays.

An object 1 cm tall is placed 30 cm in front of a convex mirror of focal length 20 cm. Find the size and position of the image formed by the convex mirror.

The shiny outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror:

Which type of spherical mirror will it provide?

The radius of curvature of a convex mirror used as a rear view mirror in a moving car is 12.0 m. A truck is coming from behind it at a distance of 3.54 m. Calculate (a) position, and (b) size of the image relative to the size of the truck. What will be the nature of the image?

A convex mirror used as a rear-view mirror in a car has a radius of curvature of 3 m. If a bus is located at a distance of 5 m from this mirror, find the position of image. What is the nature of the image?

A man standing in front of a special mirror finds his image having a very small head, a fat body and legs of normal size. What is the shape of:

(a) top part of the mirror?
(b) middle part of the mirror?
(c) bottom part of the mirror?

Name the spherical mirror which can produce a real and diminished image of an object.

The diagrams show the appearance of a fork when placed in front of and close to two mirrors A and B, turn by turn.
Figure

(a) Which mirror is convex
(b) Which mirror is concave

Whatever be the position of the object, the image formed by a mirror is virtual, erect and smaller than the object. The mirror then must be:

(a) plane
(b) concave
(c) convex
(d) either concave or convex

Draw a labelled ray diagram to show the formation of image in a convex-mirror when the object is at infinity. Mark clearly the pole and focus of the mirror in the diagram.

If a driver has one convex and one plane rear-view mirror, how would the images in each mirror appear different?

Describe with the help of a ray-diagram, the size, nature and position of the image formed by a convex lens when an object is placed beyond 2f in front of the lens.

f the image formed by a convex lens is of the same size as that of the object, what is the position of the image with respect to the lens?

Explain with the help of a diagram, why the convex lens is also called a converging lens.

Linear magnification (m) produced by a rear view mirror fitted in vehicles:

(a) is equal to one
(b) is less than one
(c) is more than one
(d) can be more less than one depending on the position of object

In order to obtain a magnification of, −0.6 (minus 0.6) with a concave mirror, the object must be placed:

(a) at the focus
(b) between pole and focus
(c) between focus and centre of curvature
(d) beyond the centre of curvature

What would your image look like if you stood close to a large:

convex mirror?

What is the advantage of using a convex mirror as  rear-view mirror in vehicles as compared to a plane mirror? Illustrate your answer with the help of labelled diagrams.

What type of mirror should be used:

as a shaving mirror?

What type of image/images are formed by:

a concave mirror?

An object is placed 15 cm from (a) a converging mirror, and (b) a diverging mirror, of radius of curvature 20 cm. Calculate the image position and magnification in each case.

What kind of mirrors are used in big shopping centres to watch the activities of the customers?

The optical prescription for a pair of spectacles is :
Right eye : −3.50 D
Left eye : −4.00 D

Are these lenses thinner at the middle or at the edges?

If a magnification of, −1 (minus one) is to be obtained by using a converging mirror, then the object has to be placed:

(a) between pole and focus
(b) at the centre of curvature
(c) beyond the centre of curvature
(d) at infinity

If the image formed is always virtual, the mirror can be:

(a) concave or convex
(b) concave or plane
(c) convex or plane
(d) only convex

The mirror used by a dentist to examine the teeth of a person is:
(d) any one of the above

(a) convex
(b) concave
(c) plane
(d) any one of the above

In order to obtain a magnification of −2 (minus 2) with a concave mirror, the object should be placed:

(a) between pole and focus
(b) between focus and centre of curvature
(c) at the centre of curvature
(d) beyond the centre of curvature

Shaving mirrors, Car headlight mirror, Searchlight mirror, Driving mirror, Dentist's inspection mirror, Touch mirror, Staircase mirror in a double-decker bus, Make-up mirror, Solar furnace mirror, Satellite TV dish, Shop security mirror.

Which of the following are concave mirrors and which convex mirrors?

Magnification produced by a convex mirror is always:

(a) more than 1
(b) less than 1
(c) equal to 1
(d) more or less than 1

Draw and complete the following diagrams to show what happens to the beams of light as they enter the glass block and then leave it:

Linear magnification produced by a concave mirror may be:

(a) less than 1 or equal to 1
(b) more than 1 or equal than 1
(c) less than 1, more than 1 or equal to 1
(d) less than 1 or more than 1

What type of image/images are formed by:

a convex mirror?

At what distance from a concave mirror of focal length 10 cm should an object be placed so that:

its virtual image is formed 20 cm from the mirror?

What do the ciliary muscles do when you are focusing on a nearby object?

Between which two points of concave mirror should an object be placed to obtain a magnification of:

(a) −3
(b) +25
(c) −0.4

The diagram given alongside shows a ray of light entering a rectangular block of glass.

(a) Copy the diagram and draw the normal at the point of entry.
(b) Draw the approximate path of the ray of light through the glass block and out of the other side.

An object is 24 cm away from a concave mirror and its image is 16 cm from the mirror. Find the focal length and radius of curvature of the mirror, and the magnification of the image.

An object is 24 cm away from a concave mirror and its image is 16 cm from the mirror. Find the focal length and radius of curvature of the mirror, and the magnification of the image.

An object is 24 cm away from a concave mirror and its image is 16 cm from the mirror. Find the focal length and radius of curvature of the mirror, and the magnification of the image.

If a ray of light goes from a rarer medium to a denser medium, will it bend towards the normal or away from it?

A man holds a spherical shaving mirror of radius of curvature 60 cm, and focal length 30 cm, at a distance of 15 cm, from his nose. Find the position of image, and calculate the magnification.

A ray of light travelling in water emerges into air. Draw a ray-diagram indicating the change in its path.

What is meant by 'refraction of light'? Draw a labelled ray diagram to show the refraction of light.

Refractive indices of water, sulphuric acid, glass and carbon disulphide are 1.33, 1.43, 1.53 and 1.63 respectively. the light travels slowest in:

(a) sulphuric acid
(b) glass
(c) water
(d) carbon disulphide

What is the speed of light in a medium of refractive index 6/5 if its speed in air is 3,00,000 km/s?

Give three examples of materials that refract light rays. What happens to the speed of light rays when they enter these materials?

Which of the following can form a virtual image which is always smaller than the object?
(a) a plane mirror
(b) a convex lens
(c) a concave lens
(d) a concave mirror

With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.

With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.

A diverging mirror of radius of curvature 40 cm forms an image which is half the height of the object. Find the object and image positions.

What type of image is always made by a concave lens?

S