Optics Question 637
Question: Focal length of a converging lens in air is R. If it is dipped in water of refractive index 1.33, then its focal length will be around (Refractive index of lens material is 1.5)
[RPMT 1997; EAMCET (Med.) 1995]
Options:
A) R
B) 2R
C) 4R
D) R / 2
Show Answer
Answer:
Correct Answer: C
Solution:
$ \frac{f _{l}}{f _{a}}=\frac{ _{a}{\mu _{g}}-1}{ _{l}{\mu _{g}}-1} $
Therefore $ f _{l}=4R $
