The refractive index of the medium is:

$A$ rectangular glass slab $ABCD$,of refractive index $n_1$,is immersed in water of refractive index $n_2$ $(n_1 > n_2)$. $A$ ray of light is incident at the surface $AB$ of the slab as shown. The maximum value of the angle of incidence $\alpha_{max}$,such that the ray comes out only from the other surface $CD$,is given by

$A$ ray of light is incident at an angle $i$ from a denser to a rarer medium. The reflected and the refracted rays are mutually perpendicular. The angle of reflection is $r$ and the angle of refraction is $r'$. Then the critical angle $C$ will be:

An optical fibre consists of a core of refractive index $\mu_1$ surrounded by a cladding of refractive index $\mu_2 < \mu_1$. $A$ beam of light enters from air at an angle $\alpha$ with the axis of the fibre. The highest angle $\alpha$ for which the ray can travel through the fibre is:

$A$ parallel beam of light is incident on a glass prism in the shape of a quarter cylinder of radius $R=0.05 \ m$ and refractive index $n=1.5$,placed on a horizontal table as shown in the figure. Beyond the cylinder,a patch of light is found whose nearest distance $x$ from the cylinder is

$A$ beam of light is incident from air on the surface of a liquid. The angle of incidence is $\theta$ and the angle of refraction is $\alpha$. If the critical angle for the liquid when surrounded by air is $\theta_c$,then $\sin \theta_c$ is: