$A$ transparent medium shows a relationship between $\sin i$ and $\sin r$ as shown in the graph. If the speed of light in vacuum is $c$,the Brewster angle for the medium is: (in $^{\circ}$)

The angle of polarisation for a medium with respect to air is $60^{\circ}$. The critical angle of this medium with respect to air is

If the polarizing angle for a medium is $60^\circ$,then the critical angle for that medium is . . . . . .

Unpolarised light is incident on the boundary between two dielectric media,whose dielectric constants are $2.8$ (medium $1$) and $6.8$ (medium $2$),respectively. To satisfy the condition that the reflected and refracted rays are perpendicular to each other,the angle of incidence should be $\tan ^{-1}\left(1+\frac{10}{\theta}\right)^{\frac{1}{2}}$. The value of $\theta$ is $.............$ (Given for dielectric media,$\mu_{r}=1$)

$A$ person lives in a high-rise building at a height of $30 \ m$ on the bank of a river. Across the river is a well-lit tower of height $60 \ m$. When the person looks through a polarizer at an appropriate angle at light from the top of the tower reflecting from the river surface,he finds the intensity of light is least. If the refractive index of water is $\frac{4}{3}$,the width of the river is ...... $m$.

When the angle of incidence on a material is $60^\circ,$ the reflected light is completely polarized. The velocity of the refracted ray inside the material is (in $m/s$)