Question

A thin plano-convex lens acts like a concave mirror of focal length 0.2 m, when silvered on its plane surface. The refractive index of the lens material is 1.5. The radius of curvature of the convex surface of the lens will be-

• A. 0.1 m
• B. 0.2 m
• C. 0.4 m
• D. 0.8 m

Answer 1

Answer: (B)

0.2 m

Answer 2

f = – $\frac { \mathrm { R } } { 2 ( \mu - 1 ) }$ \ – 0.2 = –

\ R = 0.2 m