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

Answer

C

Explanation

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