Optics Question 695
Question: A thin glass (refractive index 1.5) lens has optical power of $ -5D $ in air. It’s optical power in a liquid medium with refractive index 1.6 will be
[AIEEE 2005]
Options:
A) 25 D
B) ? 25 D
C) 1 D
D) None of these
Show Answer
Answer:
Correct Answer: D
Solution:
$ \frac{f _{l}}{f _{a}}=\frac{{( _{a}}{\mu _{g}}-1)}{{( _{l}}{\mu _{g}}-1)} $
Therefore $ \frac{f _{l}}{f _{a}}=\frac{ _{a}{\mu _{g}}-1}{ _{l}{\mu _{g}}-1}=\frac{1.5-1}{\frac{1.5}{1.6}-1}=\frac{0.5\times 1.6}{-0.1}=-8 $
Therefore $ P _{l}=\frac{P _{a}}{8}=\frac{5}{8} $
