Light travels through a glass plate of thickness $t$ having refractive index $\mu$. If $c$ be the velocity of light in vacuum, time taken by the light to travel through this thickness of glass is :

The correct option is C $\frac{\mu t}{c}$
The velocity of light in a medium of refractive index $\mu$ is $\frac{c}{\mu }$.

Hence the time taken by light in this medium to travel through the thickness of glass is $\frac{t}{v}=\frac{t}{c/\mu }$

$=\frac{\mu t}{c}$