Q. 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 $2\ f$
C) Concave mirror of focal length $\frac{f}{2}$
D) None of the above
Explanation
(c) Focal length of effective lens
$\frac{1}{F} = \frac{2}{f_{l}} + \frac{1}{f_{m}} = \frac{2}{f_{l}} + \frac{1}{\infty} \Rightarrow F = \frac{f_{l}}{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.