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Selina solutions for Class 8 Physics chapter 5 - Light Energy

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

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Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

Chapter 5: Light Energy

Chapter 5: Light Energy solutions [Page 0]

Write true or false 

Water is optically denser than glass.

Write true or false

A ray of light when passes from glass to air, bends towards the normal.

 Write true or false

The speed of light is more in glass than in water.

Write true or false

 The depth of a pond when seen from above appears to be less.

Write true or false 

Light travels at a lower speed in water than in air.

 Write true or false 

Light travels in the same straight line path while passing through different media.

 Write true or false 

At the point of incidence, a line drawn at right angles to the surface, separating the two media, is called the normal.

 Write true or false 

 The angle formed between the normal and the refracted ray is known as the angle of incidence.

 

 Write true or false 

 At the point of incidence, a line drawn at right angles to the surface, separating the two media, is called the normal.

 Write true or false 

 Image is formed by a mirror due to refraction of light.

Write true or false 

Rays of light incident parallel to the principal axis pass through the focus after reflection from a concave mirror.

Write true or false 

 A convex mirror is used as a shaving mirror.

 Write true or false 

The focal length of a convex mirror is equal to its radius of curvature.

 Write true or false

The focal length of a convex mirror is equal to its radius of curvature.

Write true or false 

 A concave mirror converges the light-rays, but a convex mirror diverges them.

 Write true or false 

 A virtual image formed by a spherical mirror is always erect and situated behind the mirror.

Write true or false 

A virtual image formed by a spherical mirror is always erect and situated behind the mirror.

 Fill in the blank

Water is opitcally .......... than air.

Fill in the blank

 Air is optically .......... than glass.

 Fill in the blank

  When a ray of light travels from water to air, it bends .............the normal.

 Fill in the blank

 When a ray of light travels from air to glass, it bends .......... the normal.

 Fill in the blank

 When white light passes through a prism, it ............

 Fill in the blank

 The splitting of white light into its constituent colours is called .............

 Fill in the blank

A .............. mirror is obtained on silvering the outer surface of a part of a hollow glass sphere.

 Fill in the blank

Radius of curvature of a spherical mirror is .............its focal length.

 Fill in the blank

 The angle of incidence for a ray of light passing through the centre of curvature of a spherical mirror is .......

 Fill in the blank

A ............ mirror always forms a virtual image.

 Fill in the blank

A concave mirror forms a virtual image for an object placed ...............................

Match the Following

                                 Column A   Column B 
(a) white Light  (1) Convex mirror
(b) Refraction (2) Concave mirror
(c) Virtual images  (3) refraction
(d) Real images  (4)  spectrum
(e) Prism (5) ray of light from glass to air 

Select the correct alternative

The speed of light in air or vacuum is

  1. 3 × 10M s-1
  2.  2.25 × 108 m s-1
  3.  332 ms-1
  4.  2.0 × 108 ms-1

 Select the correct alternative

A ray of light moving from an optically rarer to a denser medium

  1.  bends away from the normal
  2.  bends towards the normal
  3.  remains undeviated
  4.  none of the above

Select the correct alternative

The angle between the normal and refracted ray is called

  1.  angle of deviation
  2.  angle of incidence
  3.  angle of refraction
  4.  angle of emergenc

Select the correct alternative

The property of splitting of white light into its seven constituent colours is known as

  1.  rectilinear propagation
  2.  refraction
  3.  reflection
  4.  dispersion

 Select the correct alternative

 The seven colours in the spectrum of sunlight in order, are represented as :

  1.  VIBGYOR
  2.  VIGYBOR
  3.  BIVGYOR
  4.  RYOBIVG

Select the correct alternative

 A ray of light passing through centre of curvature of a spherical mirror, after reflection

  1. passes through the focus
  2.  passes through the pole
  3.  becomes parallel to the principal axis
  4.  retraces its own path.

  Select the correct alternative

If the radius of curvature of a concave mirror is 20 cm, its focal length is:

  1. 10 cm
  2.  20 cm
  3.  40 cm
  4.  80 cm

Select the correct alternative

The image formed by a convex mirror is

  1.  erect and diminished
  2.  erect and enlarged
  3.  inverted and diminished
  4.  inverted and enlarged.

Select the correct alternative

The image formed by a concave mirror is of the same size as the object, if the object is placed

  1. at the focus
  2. between the pole and focus
  3.  between the focus and centre of curvature
  4.  at the centre of curvature.

Select the correct alternative

A convex mirror is used

  1.  as a shaving mirror
  2.  as a head mirror by a dentist
  3.  as a rear view mirror by a driver
  4.  as a reflector in torch.

Chapter 5: Light Energy solutions [Page 0]

1. State the speed of light in (a) air, (b) water, and (c) glass

How does the speed of light determine the optical density of a medium ?

Which is optically denser : water or air ? Give reason

Out of air and glass, which is optically rarer ? Give reason.

What do you understand by refraction of light ?

Describe an experiment to show that a light ray bends when it passes from one transparent medium into another transparent medium.

Draw a ray diagram to show that the depth of a vessel containing water when seen from above, appears to be less than its real depth.

Define the following terms :
Incident ray, Refracted ray, Angle of incidence, Angle of refraction.

A ray of light falls normally on a glass slab. What is the angle of incidence ?

A ray of light travels from a rarer medium to a denser medium. How will it bend ?

A ray of light travels from a denser medium to a rarer medium. How will it bend ?

Draw a diagram showing the refraction of a light ray from water to glass. Label on it the incident ray, the angle of incidence (/), and the angle of refraction (r)

The diagram given below in fig shows a ray of light AO falling on a surface separating two media. Draw the refracted ray in each, case.

The diagram in figure shows a ray of light AO falling on a rectangular glass slab PQRS. Complete the diagram till the ray of light emerges out of the slab. Label on the diagram the incident ray, the refracted ray and the emergent ray.

Explain the following :
(a) A coin placed at the bottom of a vessel appears to be raised when water is poured in the vessel.
(b) A straight stick partly dipped in water obliquely, appears to be bent at the surface of water.
(c) The sun is seen before the sunrise and after the sunset.

What is mirage ? Give a reason for its formation ?

What is a prism ? Draw a ray diagram to show7 the refraction of a light ray through a prism.

What do you mean by the term dispersion ?

A ray of white light falls on a prism. Draw a ray diagram to show that the prism disperses the white light.

In figure AO is the ray of white light falling on a prism PQR. Complete the diagram till the light emerges out from the prism and falls on the screen.

What do you understand by the term spectrum ? Name the various colours present in the spectrum of sunlight.

You are given a disc divided into seven sectors with colours violet, indigo, blue, green, yellow, orange and red in them. What would be its colour when it is rotated rapidly ?

State the two laws of reflection of light. Ans. Laws of reflection :

What is a spherical mirror ?

State the two kinds of spherical mirror and distinguish them with the aid of proper diagrams.

Explain the following terms :
Pole, Centre of curvature, Radius of curvature, Principal axis. Show them on separate diagrams for each of the concave and convex mirrors

What do you understand by the focus and focal length of a spherical mirror ? Show them on the separate diagrams for each of a concave mirror and a convex mirror.

Draw suitable diagrams to illustrate how a beam of light incident parallel to the principal axis is reflected by:
(a) a concave mirror, and (b) a convex mirror

How is a spherical mirror used to converge a beam of light at a point ? Name the type of mirror used.

How is a spherical mirror used to diverge a beam of light from a point ? Name the type of mirror used.

State the direction of incident ray which after reflection from a spherical mirror gets reflected along its own path. Give a reason.

How is the focal length of a spherical mirror related to its radius

The diagram (figure) given below shows two parallel rays 1 and 2 incident on (a) a concave mirror, (b) a convex mirror. Draw the reflected rays and mark the focus by the symbol F.

Complete the following diagrams in figure by drawing the reflected rays for the incident rays 1 and 2 if F is the focus and C is the centre of curvature.

Which are the two convenient rays that are chosen to construct the image by a spherical mirror for a given object ? Explain with the help of suitable ray diagrams.

Draw a ray diagram to show the formation of image of an object placed beyond the centre of curvature of a concave mirror. State the position, size and nature of the image.

Draw a ray diagram to show the formation of image of an object placed at the centre of curvature of a concave mirror. State the position, size and nature of the image.

Draw a ray diagram to show the formation of image of an object placed between the focus and centre of curvature of a concave mirror. State the position, size and nature of the image.

Draw a ray diagram to show the formation of image of an object placed between the pole and focus of a concave mirror. State the position, size and natu re of the image.

Draw a ray diagram to show the formation of image of an object placed on the principal axis of a convex mirror. State the position, size and nature of the image. What happens to the image as the object is moved away from the mirror ?

Draw separate diagrams for the formation of virtual image of an object by (a) concave mirror and (b) convex mirror.
State the difference in the two images

Name the mirror which always forms an erect and virtual image. What is the size of the image as compared to that of the object ?

Name the mirror which forms an erect, virtual and enlarged image of an object. What is the position of object relative to the mirror ?

What is a real image ? Name the mirror which can be used to obtain the real image of an object. What should be the position of the object relative to the mirror ?

How can a concave mirror be used to obtain a virtual image of an object ? Draw a diagram to illustrate your answer.

State two uses of a concave mirror.

State two uses of a convex mirror.

A driver uses a convex mirror as a rear view mirror. Explain the reason with the help of a ray diagram.

State the kind of mirror used
(a) by a dentist, and
(b) as a street light reflector.

Name the kind of mirror used to obtain
(a) a real and enlarged image
(b) a virtual ard enlarged image
(c) a real and diminished image, and
(d) a virtual and diminished image.

Chapter 5: Light Energy

Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

Selina solutions for Class 8 Physics chapter 5 - Light Energy

Selina solutions for Class 8 Physics chapter 5 (Light Energy) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Selina Concise Physics - Middle School for Class 8 (2018-19 Session) solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com are providing such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 8 Physics chapter 5 Light Energy are Concept of Refraction, Curved Mirrors - Convex, Curved Mirrors - Concave, Reflecting Surface (Convex and Concave), Uses of Curved Mirrors, Terms Related to Curved Mirrors:Focus, Principal Axis, Centre of Curvature, Radius of Curvature, Rules for Making Ray Diagrams of Spherical Mirrors, Real and Virtual Images, Ray Diagrams with Curved Mirrors Where Real Images Are Formed, Dispersion of White Light into Constituent Colours.

Using Selina Class 8 solutions Light Energy exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Selina Solutions are important questions that can be asked in the final exam. Maximum students of CISCE Class 8 prefer Selina Textbook Solutions to score more in exam.

Get the free view of chapter 5 Light Energy Class 8 extra questions for Physics and can use Shaalaa.com to keep it handy for your exam preparation

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