A lens if placed between a source of light and a wall. It forms images of area` A_(1)` and `A_(2)` on the wall for its two different positions. The area of the source or light is

Options

A. `(A_(1)+A_(2))^(1//2)`
B. `[(1)/(A_(1))+(1)/(A_(2))]^(-1)`
C. `sqrt(A_(1)A_(2))`
D. `[sqrt(A_(1))+sqrt(A_(2))]^(2)`

Answer

C

Explanation

This is an extension of `d=sqrt(d_(1)d_(2))` for displacement method `A=sqrt(A_(1)A_(2))`.