RRB Technician 2013 Ques 6
Question: The plane surface of a plano-convex lens is silvered. Focal length of lens is f. After silvering, it will behave as
Options:
A) plane mirror
B) convex mirror of focal length 2f
C) concave mirror of focal length $ \frac{f}{2} $
D) None of the above
Show Answer
Answer:
Correct Answer: C
Solution:
- When plane surface of a plano-convex lens is silvered, it behaves like a concave mirror. Radius of curvature of concave mirror so formed becomes equal to focal length of plano-convex lens.
$ \therefore $ f of mirror $ =\frac{1}{2}\times $ Focal length of lens Focal length of mirror $ =\frac{f}{2} $
BETA
