Question

The plane surface of a plano-convex lens of focal length f is silvered. It will behave as –

• A. Plane mirror
• B. Convex mirror of focal length 2f
• C. Concave mirror of focal length f/2
• D. None of these

Answer 1

Answer: (C)

Concave mirror of focal length f/2

Answer 2

F_l = F, F_m = 

= $\frac { 2 } { \mathrm {~F} _ { \ell } }$ + $\frac { 1 } { \mathrm {~F} _ { \mathrm { m } } }$ = + $\frac { 1 } { \infty }$

Ž concave mirror