Optics Question 620
Question: A thin double convex lens has radii of curvature each of magnitude 40 cm and is made of glass with refractive index 1.65. Its focal length is nearly
[MP PMT 1997]
Options:
A) 20 cm
B) 31 cm
C) 35 cm
D) 50 cm
Show Answer
Answer:
Correct Answer: B
Solution:
$ f=\frac{R}{2(\mu -1)}\Rightarrow f=\frac{40}{2(1.65-1)}\approx 31 $ cm
