If a light ray $IM$ is incident on the surface $AB$ of a rectangular glass slab as shown,identify the correct emergent ray.

Which of the following materials has maximum optical density?

The refractive index of dense flint glass is $1.65$ and for alcohol it is $1.36,$ with respect to air. What is the refractive index of dense flint glass with respect to alcohol?

The absolute refractive indices of glass and water are $4/3$ and $3/2$ respectively. If the speed of light in glass is $2 \times 10^{8} \ m \ s^{-1}$,calculate the speed of light in $(i)$ vacuum,$(ii)$ water.

Find out,from the table,the medium having the highest optical density. Also,find the medium with the lowest optical density.

Material medium	Refractive index
Air	$1.0003$
Ice	$1.31$
Water	$1.33$
Alcohol	$1.36$
Kerosene	$1.44$
Fused quartz	$1.46$
Turpentine oil	$1.47$
Benzene	$1.50$
Crown glass	$1.52$
Canada Balsam	$1.53$
Rock salt	$1.54$
Carbon disulphide	$1.63$
Dense flint glass	$1.65$
Ruby	$1.71$
Sapphire	$1.77$
Diamond	$2.42$

What will be the angle of refraction for a light ray incident normally at the surface (in $^{\circ}$)?