Draw Images in Case of a Concave Lens When the Object is at Infinity. - Physics


Draw images in case of a concave lens when the object is at infinity.



When the object is at infinity, the incident ray is taken parallel to the principal axis. As shown in the figure, the image is virtual and is formed at the focus F1 It is diminished (small) in size.

Concept: Concave Lens
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Chapter 4: Refraction through Lenses and Optical Instruments - Figure Based Long Answers


ICSE Class 10 Physics
Chapter 4 Refraction through Lenses and Optical Instruments
Figure Based Long Answers | Q 22.1


Due to gradual weakening of ciliary muscles and diminishing flexibility of the eye lens a certain defect of vision arises. Write the name of this defect. Name the type of lens required by such persons to improve the vision. Explain the structure and function of such a lens.

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 

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

Which type of lenses are: 

thinner in the middle than at the edges?

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, 

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.

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 

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

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

What kind of lens is used to correct 


Define the term principal foci of a concave lens and show them with the help of proper diagrams.


The following diagram in given below shows an object OA and its virtual image IB formed by a lens.

a) name the lens which always forms an erect and virtual image.
(b) state whether the image in part (a) is magnified or diminished.

State the changes in the position, size and nature of the image of an object when brought from infinity up to a concave lens. Illustrate your answer by drawing ray diagrams.

State whether the following statement are ‘true’ or ‘false’ by writing T/F against them.

A concave lens, if kept at a proper distance from an object, can form its real image.

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.

An object is placed at a distance 24 cm in front of a convex lens of focal length 8 cm.

(i) What is the nature of the image so formed ?
(ii) Calculate the distance of the image from the lens.
(iii) Calculate the magnification of the image.

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

Which lens is converging:

A concavo-convex lens or a convexo-concave lens?

A concave lens forms the image of an object kept at a distance 20 cm in front of it, at a distance 10 cm on the side of the object.

What is the nature of the image?

Find the focal length of the lens.

Choose the correct alternative and rewrite the following: 

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

Convex lens : converging : : concave lens : _______

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

Distinguish between Concave lens and Convex Lens.

Distinguish between:

Concave Lens and Convex Lens


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