Optics Question 668
Question: The focal length of lens of refractive index 1.5 in air is 30 cm. When it is immersed in a liquid of refractive index $ \frac{4}{3} $ , then its focal length in liquid will be
[BHU 2002]
Options:
A) 30 cm
B) 60 cm
C) 120 cm
D) 240 cm
Show Answer
Answer:
Correct Answer: C
Solution:
By using $ \frac{f _{l}}{f _{a}}=\frac{{( _{a}}{\mu _{g}}-1)}{{( _{l}}{\mu _{g}}-1)}\Rightarrow f _{w}=4f _{a}=4\times 30 $ =120 cm.
