Question

An object is placed at distance of $64cm$ from a white screen. By placing a convex lens at a distance of $32cm$ from the object, it is found that a distinct image of the object is formed on the screen. Calculate the focal length of the lens?

Answer 1

Given:$v=32cm$ $u=-32cm$ (convex lens)

To find: $f$

Solution: From lens formula

$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

$\frac{1}{32}+\frac{1}{32}=\frac{1}{f}$

$f=16cm$