A concave mirror 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 mirror combination retuens to infinity. The distance d must equal

Options

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

Answer

C

Explanation

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