Optics Question 610
Question: A plano convex lens $ (f=20cm) $ is silvered at plane surface. Now f will be
[BHU 1995; DPMT 2001; MP PMT 2005]
Options:
A) 20 cm
B) 40 cm
C) 30 cm
D) 10 cm
Show Answer
Answer:
Correct Answer: D
Solution:
$ \frac{1}{F}=\frac{2}{f _{l}}+\frac{1}{f _{m}} $
$ \Rightarrow $ $ \frac{1}{F}=\frac{2}{20}+\frac{1}{\infty }\Rightarrow F=10 $ $ cm $
