Why is the brilliance of a diamond observed?

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

$A$ ray of light travels from a denser medium to a rarer medium. The reflected and the refracted rays are perpendicular to each other. If '$i$' and '$r_1$' are the angle of incidence and angle of refraction respectively and '$C$' is the critical angle,then the angle of incidence is

Explain the phenomenon of total internal reflection in a right-angled prism.

$A$ jar of height $h$ is filled with a transparent liquid of refractive index $\mu$. At the centre of the jar on the bottom surface is a dot. Find the minimum diameter of a disc,such that when placed on the top surface symmetrically about the centre,the dot is invisible.

The critical angle of a medium for a specific wavelength,if the medium has relative permittivity $3$ and relative permeability $\frac{4}{3}$ for this wavelength,will be.....$^o$