A Lens Always Forms an Image Between the Object and the Lens. - Physics

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A lens always forms an image between the object and the lens.

state three characteristics of the image.



The image formed is virtual, erect and diminished.

Concept: Convex Lens
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Chapter 5: Refraction through a Lens - Exercise 5 (B) 1 [Page 120]


Selina Concise Physics Class 10 ICSE
Chapter 5 Refraction through a Lens
Exercise 5 (B) 1 | Q 12.3 | Page 120


Draw a ray diagram to show the formation of image in the above situation

A student wants to project the image of a candle flame on the walls of school laboratory by using a lens:-

(a) Which type of lens should be use and why?

(b) At what distance in terms of focal length 'F' of the lens should be place the candle flame so as to get (i) a magnified, and (ii) a diminished image respectively on the wall?

(c) Draw ray diagram to show the formation of the image in each case?

A student has obtained a magnified image of a flame on a screen using a convex lens. To draw the corresponding ray diagram to show the image formation, which of the following two rays whose paths after refraction are shown, should he select ?

(A) I and II

(B) II and III

(C) III and IV

(D) I and III

Complete the following table:

Instrument Number of Convex
Simple Microscope .............. ..............
Compound Microscope .............. ..............
Telescope .............. ..............

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.

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? 

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. 

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

 Complete the following sentence.

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

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?

A ray of light incident at a point on the principal axis of a convex lens passes undeviated through the lens.
(a) What special name is given to this point on the principal axis?
(b) Draw a labelled diagram to support your answer in part (a)

Study the diagram below.

Complete the diagram to form the image of the object AB.

Give two characteristic of the virtual image formed by a convex lens.

Complete the following sentence:

an object is placed at a distance 5 cm from a convex lens of focal length 10 cm. The image formed is virtual, upright and …………….

Out of the five incident rays shown in the figure find the three rays that are obeying the laws of refraction and may be used for locating the position of image formed by a convex lens:

(A) 1, 2 and 3

(B) 2, 3 and 4

(C) 3, 4 and 5

(D) 1, 2 and 4

Distinguish between:

Concave lens and Convex lens

i. Which type of microscope has the arrangement of lenses shown in the  adjoining figure?
ii. Label the figure correctly.
iii. Write the working of this microscope.
iv. Where does this microscope used?
v. Suggest a way to increase the efficiency of this microscope.

The image obtained while finding the focal length of convex lens is ....................

Observe the following figure and answer the questions.

a) Which optical instrument shows arrangement of lenses as shown in the figure?
b) Write in brief the working of this optical instrument.
c) How can we get different magnifications in this optical instrument?
d) Draw the figure again and labelled it properly

Observe the following figure and complete the table:

Points Answer
(i) Position of the object  
(ii) Position of the image  
(iii) Size of the image   
(iv) Nature of the image  

A lens forms the image of an object placed at a distance 15 cm from it, at a distance 60 cm in front of it. Find :  the magnification.

If an object is placed in front of a convex lens beyond 2F1, then what will be the position, relative size, and nature of an image which is formed? Explain with a ray diagram.

Rewrite the following statement by selecting the correct option:
The power of a convex lens is 2.5 dioptres. Its focal length is ______________.

Point out the difference between a convex lens and a concave lens.

Which lens can produce a real and inverted image of an object?

Draw a diagram to show the convergent action of a convex lens by treating it as a combination of glass block and two triangular glass prisms, with the aid of two parallel incident rays.

Where should an object be placed in front of a convex lens so as to form an inverted and enlarged image? Will the image be real or virtual? Draw a ray diagram to illustrate your answer.

In the figure given below L is a convex lens, M is a plane mirror and S is a point source of light. Rays of light from the source S return to their point of origin. Complete the ray diagram to show this. What is the point S called?

For a specific glass lens f = 0.5 m. This is the only information given to the student. Which type of lens is given to him and what is its power?

_______ times larger images can be obtained by using a simple microscope.

_______ is a combination of two convex lenses with small focal length.

Object at 2F1 of a convex lens : Image at 2F2 : : Object at F1 : _______

Simple microscope : Number of convex lens one : : compound microscope : _______

: Object near the lens : : ______ :

Find the odd one out and give its explanation.

Find the odd one out and give its explanation.

Write the name.

The lens used in simple microscope.

Write scientific reason.

Adults need bifocal lens spectacle.

Observe the given figure and answer the following questions.

  1. Where is the above type of lens construction used?
  2. What type of image is formed by an objective lens?
  3. What happens instead of placing at Fo if the object is placed in between O and Fo?

Differentiate convex lens and concave lens.

  1. In which type of microscope do you find the lens arrangement as shown in the following diagram?
  2. Write about the working and the use of this microscope.

Distinguish between Concave lens and Convex lens.

Distinguish between:

Concave lens and Convex Lens

Distinguish between Concave lens and Convex Lens.

Distinguish between:

Concave lens and Convex Lens

Distinguish between:

Concave lens and Convex Lens


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