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A screen is placed 90 cm away from an o...

A screen is placed 90 cm away from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20 cm. Find the focal length of lens.

Text Solution

Verified by Experts

By the displacement method
`f=(d^2-x^2)/(4d)= f=(90^2-20^2)/( 4 times 90)= 21.4 cm`
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