If one face of a prism of prism angle $30^{\circ}$ and refractive index $\mu = \sqrt{2}$ is silvered,the incident ray retraces its initial path. The angle of incidence is.......$^{\circ}$

An equilateral prism deviates a ray through $40^{\circ}$ for two angles of incidence differing by $20^{\circ}$. The possible angles of incidence are:

$A$ glass prism has a right-triangular cross-section $ABC$,with $\angle A=90^{\circ}$. $A$ ray of light parallel to the hypotenuse $BC$ and incident on the side $AB$ emerges grazing the side $AC$. Another ray,again parallel to the hypotenuse $BC$,incident on the side $AC$ suffers total internal reflection at the side $AB$. Which one of the following must be true about the refractive index $\mu$ of the material of the prism?

Explain the minimum deviation angle for a prism using the graph of deviation angle versus incidence angle.

$A$ triangular prism of glass is shown in the figure. $A$ ray incident normally to one face is totally reflected,if $\theta = 45^o$. The index of refraction of glass is

$A$ ray of light passes through an equilateral prism $(\mu = 1.5)$ such that the angle of incidence is equal to the angle of emergence,and the latter is equal to $3/4$ of the prism angle. The angle of deviation is.......$^o$