The reason for the shining of an air bubble in water is

$A$ point source of light is placed $4 \; m$ below the surface of water of refractive index $5/3$. The minimum diameter of a disc which should be placed over the source on the surface of water to cut-off all light coming out of water is ... $m$.

If light travels a distance $x$ in time $t_1$ sec in air and $10x$ distance in time $t_2$ sec in a certain medium,then find the critical angle of the medium.

The radius of the light circle observed by a fish at a depth of $12 \ m$ is (refractive index of water $\mu = 4/3$):

The critical angle of light passing from glass to air is minimum for which wavelength?

$A$ beam of light consisting of red,green and blue colours is incident on a right-angled prism on face $AB$. The refractive indices of the material for the above red,green and blue colours are $1.39, 1.44$ and $1.47$ respectively. $A$ person looking on surface $AC$ of the prism will see