An infinitely long rod lies along the axis of a concave mirror of focal length f. The near end of the rod is distance `u gt f` from the mirror. Its image will have length

Options

A. `(f^(2))/(u-f)`
B. `(uf)/(u-f)`
C. `(f^(2))/(u+f)`
D. `(uf)/(u+f)`

Answer

A

Explanation

`u_(I) =- u,v_(1) =- ((uf)/(u-f))`
`u_(2) = oo, v_(2) =- f`
`|v_(2)|-|v_(1)| = (uf)/(u-f) -f = (uf-uf+f^(2))/(u-f) = (f^(2))/(u-f)`