Question

A converging beam of rays in incident on a diverging lens. Having passed through the lens the rays intersect at a point `15 cm` from the lens. If the lens is removed, the point where the rays meet, move `5 cm` closer to the mounting that holds the lens. Find the focal length of the lens.
A. `-30cm`
B. `5cm`
C. `-10cm`
D. 20cm

Answer 1

Correct Answer - A

`(1)/(f)=(1)/(v)-(1)/(u)=(1)/(15)-(1)/(10)=(-1)/(30)`
`f=-30cm`