When the object is at distance `mu_1 and mu_2` from the optical centre of a convex lens, a real and a virtual image of the same magnification are obtained. The focal length of the lens is

Options

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

Explanation

Use `m_(1)=m_(2)`