Optics Question 447
Question: Consider an equiconvex lens of radius of curvature R and focal length $ f. $ If $ f>R $ , the refractive index $ \mu $ of the material of the lens
Options:
A) Is greater than zero but less than 1.5
B) Is greater than 1.5 but less than 2.0
C) Is greater than 1.0 but less than 1.5
D) None of these
Show Answer
Answer:
Correct Answer: C
Solution:
[c] $ \frac{1}{f}=(\mu -1)( \frac{2}{R} ) $ Or $ f=\frac{R}{2(\mu -1)} $ Now, $ f>R $
$ \therefore \frac{R}{2(\mu -1)}>R $ Or $ \frac{1}{2(\mu -1)}>1 $ or $ 2(\mu -1)<1 $ Or $ \mu -1<\frac{1}{2} $ or $ \mu <( 1+\frac{1}{2} ) $ or $ \mu <1.5 $
