A concave mirrorr of focal length `f_(1)` is placed at a distance of `d` from a convex lens of focal length `f_(2)`. A beam of light coming from infinity and falling on this convex lens-concave mirrorr combination returns to infinity. The distance `d` must equal.

Options

A. `-2f_(1)+f_(2)`
B. `f_(1)+f_(2)`
C. `-f_(1)+f_(2)`
D. `2f_(1)+f_(2)`

Answer

D

Explanation

`d=2f_(1)+f_(2)`