Physics

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.

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

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

(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 :

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

Power of the lens is +4 Dioptre

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