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

An ice cube has a bubble inside. When viewed from one side,the apparent distance of the bubble is $12 \ cm$. When viewed from the opposite side,the apparent distance of the bubble is observed as $4 \ cm$. If the side of the ice cube is $24 \ cm$,the refractive index of the ice cube is $.....$.

$A$ glass slab of thickness $3 \, cm$ and refractive index $3/2$ is placed on an ink mark on a piece of paper. The mark is viewed from a distance of $5.0 \, cm$ above the top surface of the slab. At what distance (in $cm$) will the mark appear to be?

$A$ microscope is focused on a mark on a piece of paper and then a slab of glass of thickness $3\, cm$ and refractive index $1.5$ is placed over the mark. How should the microscope be moved to get the mark in focus again?

Consider the situation shown in the figure. Water $\left( \mu_w = \frac{4}{3} \right)$ is filled in a beaker up to a height of $10 \, cm$. $A$ plane mirror is fixed at a height of $5 \, cm$ from the surface of the water. The distance of the image from the mirror after reflection of an object $O$ at the bottom of the beaker is......$cm$.

When the same monochromatic ray of light travels through a glass slab and through water,the number of waves in a glass slab of thickness $6 \ cm$ is the same as in a water column of height $7 \ cm$. If the refractive index of glass is $1.5$,then the refractive index of water is: