How Would You Alter the Above Diagram to Show How a Converging Lens Can Produce a Beam of Parallel Rays of Light. - Science


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



When rays of light come from the focus of lens, the emergent rays of light get parallel to the principal axis.

Concept: Concave Lens
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Chapter 5: Refraction of Light - Exercise 3 [Page 242]


Lakhmir Singh Class 10 Physics (Science)
Chapter 5 Refraction of Light
Exercise 3 | Q 50.2 | Page 242


Define the principal focus of a concave lens.  

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

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


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

How would a pencil look like if you saw it through 

a concave lens  Is the image real or virtual?

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.

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. 

How does the action of a convex lens differ from that of a concave lens on a parallel beam of light incident on them? Draw diagram to illustrate your answer.

Study the following diagram :

Name the lens LL’

An object is placed on the axis of a lens. An image is formed by refraction in the lens. For all positions of the object on the axis of the lens, the positions of the image are always always between the lens and the object Draw a ray diagram to show it.

Give two characteristic of the image formed by a concave lens.

Complete the following sentence:

 An object is placed at a distance of more than 40 cm from a convex lens of focal length 20 cm. The image formed is real, inverted and ……….

If the image formed by a lens is diminished in size and erect, for all positions of the object, what type of lens is it?

Explain the working of an astronomical telescope using refraction of light.


A student obtained clear image of window grills on the screen. But the teacher told him to get the image of a tree far away, instead of window. To get a clear image,  the lens must be ............................

A virtual diminished image is formed when an object is placed between the optical centre and the principal focus of a lens.

(i) Name the type of lens which forms the above image.
(ii) Draw a ray diagram to show the formation of the image with the above stated characteristics.

Write the SI unit of focal length of a concave lens.

Distinguish between concave and convex lens.

Can a concave lens form an image of size two times that of the object? Give reason?

Choose the correct alternative and rewrite the following: 

Inside water, an air bubble behaves ....................

State three characteristics of the image of an extended source, formed by a concave lens.

In figure give below of thin concave lens, F1 and F2 are its foci, complete the path of the given ray of light after it emerges out of the lens.

Convex lens : converging : : concave lens : _______

Convex magnifying glass is called divergent magnifying glass and concave magnifying glass is called converging magnifying glass.

If the power of a lens is -4.0 D, then it means that the lens is a ______.

Distinguish between Concave lens and Convex Lens.

Distinguish between:

Concave Lens and Convex Lens


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