Q. The ratio of thickness of plates of two transparent mediums $A$ and $B$ is $6\ :4$. If light takes equal time in passing through them, then refractive index of $B$ with respect to $A$ will be
A) $1.4$
B) $1.5$
C) $1.75$
D) $1.33$
Explanation
(b) Time taken by light to travel distance $x$ through a medium of refractive index $\mu$ is
$t = \frac{\mu x}{c} \Rightarrow \frac{\mu_{B}}{\mu_{A}} = \frac{x_{A}}{x_{B}} = \frac{6}{4} \Rightarrow \ _{A}\mu_{B} = \frac{3}{2} = 1.5$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.