Q. A glass convex lens $(\mu_{g} = 1.5)$ has a focal length of $8\ cm$ when placed in air. What would be the focal length of the lens what it is immersed in water ($\mu_{\omega} = 1.33$)
A) $2\ m$
B) $4\ cm$
C) $16\ cm$
D) $32\ cm$
Explanation
(d) $\frac{f_{l}}{f_{a}} = \frac{(_{a}\mu_{g} - 1)}{(_{l}\mu_{g} - 1)}$
$\Rightarrow \frac{f_{w}}{f_{a}} = \frac{(1.5 - 1)}{\left( \frac{1.5}{1.33} - 1 \right)} \Rightarrow f_{w} = 32\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.