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ICSE Class 10 Physics Question 14 of 25

Model Paper 1 — Question 3

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Question 4(iii)

The figure given below shows the experimental set up for the determination of focal length of a lens using a plane mirror.

The diagram in figure shows experimental setup for determination of the focal length of a lens using a plane mirror. Draw two rays from the point O of the object to show the formation of image I at O itself. What is the size of the image I? State two more characteristics of the image I. Name the distance of the object O from the optical centre of the lens. To what point will the rays return if the mirror is moved away from the lens by a distance equal to the focal length of the lens? Refraction through a lens, Concise Physics Class 10 Solutions.

(a) Draw two rays from the point O of the object to show the formation of image I at O itself.

(b) What is the size of the image I?

(c) A convex lens of short focal length is used in which optical instrument?

(d) The focal length of a convex lens is 25 cm. Express its power with sign.

Answer

(a) Below ray diagram shows the formation of image I at O itself:

The diagram in figure shows experimental setup for determination of the focal length of a lens using a plane mirror. Draw two rays from the point O of the object to show the formation of image I at O itself. What is the size of the image I? A convex lens of short focal length is used in which optical instrument? The focal length of a convex lens is 25 cm. Express its power with sign. Model Paper 1, Concise Physics Class 10 Solutions.

(b) The size of the image is same as that of the object O.

(c) A convex lens of short focal length is used in a microscope to magnify small objects.

(d) Given,

Focal length of convex lens = f = + 25 cm = + 0.25 m

Power of a lens is expressed as reciprocal of its focal length in metre and written as :

P=1f=10.25=+4D\text P=\dfrac{1}{\text f}=\dfrac{1}{0.25}=+4 D

Power of the lens is +4 Dioptre