Optics Question 679
Question: A thin plano-convex lens acts like a concave mirror of focal length 0.2 m when silvered from its plane surface. The refractive index of the material of the lens is 1.5. The radius of curvature of the convex surface of the lens will be
[KCET 2004]
Options:
A) 0.4 m
B) 0.2 m
C) 0.1 m
D) 0.75 m
Show Answer
Answer:
Correct Answer: B
Solution:
$ f=\frac{R}{2(\mu -1)} $
$ \Rightarrow R=2f(\mu -1) $
$ =2\times 0.2(1.5-1) $ =0.2m.
