Home
Class 12
PHYSICS
The focal length of a thin biconvex lens...

The focal length of a thin biconvex lens is 20cm. When an object is moved from a distance of 25cm in front of it to 50cm, the magnification of its image changes from `m_(25)` to `m_(50)`. The ration `m_(25)//m_(50)` is

Text Solution

Verified by Experts

The correct Answer is:
6
`m = (f)/(f + u) implies m_(25) = (20)/(20 - 25) = -4 "and" m_(50) = (20)/(20 - 50) = -(2)/(3) implies (m_(25))/(m_(50)) = (4 xx 3)/(2) = 6`
Promotional Banner

Topper's Solved these Questions

Similar Questions

Explore conceptually related problems

The focal length of a concave mirror is 50cm. Where an object be placed so that its image is two times and inverted

Distance of an object from a concave lens of focal length 20 cm is 40 cm. Then linear magnification of the image

If a lens is moved towards the object from a distance of 40 cm to 30 cm, the magnification of the image remains the same (numarically). The focal length of the lens is

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

An object of height 2 cm is placed in front of a convex lens of focal length 20 cm at a distance of 15 cm from it. Find the position and magnification of the image.

Find distanace of image from a convex lens of focal length 20cm if object is placed at a distance of 30cm from the lens. Also find its magnification.

The focal length of a simple convex lens used as a magnifier is 10 cm. For the image to be formed at a distance of distinct vision D = 25 cm, the object must be placed away from the lens nearly at a distance of

An astronomical refractive telescope has an objective of focal length 20 m and an eyepiece of focal length 2 cm .Then the magnification

Draw a labelled ray diagram for the formation of image by a convex lens of focal length 15 cm when the object is placed at a distance of 25 cm from the lens. Determine the size of the image formed, if size of the object is 4 cm.

An object is placed at 20 cm from a convex mirror of focal length 20 cm. The distance of the image from the pole of the mirror is