A lens is 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 of light is

Options

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

Answer

C

Explanation

Area of source or light (i.e. size of object)
O = `sqrt(A_(1) A_(2))` .