Unpolarised light is incident on a plane glass surface. What should be the angle of incidence so that the reflected and refracted rays are perpendicular to each other (in $°$)?

The polarising angle for a transparent medium is $\theta$ and $V$ is the speed of light in that medium. The relation between $\theta$ and $V$ is (where $c$ is the velocity of light in vacuum):

$A$ person lives in a high-rise building on the bank of a river $50\, m$ wide. Across the river is a well-lit tower of height $40\, m$. When the person,who is at a height of $10\, m$,looks through a polarizer at an appropriate angle at light of the tower reflecting from the river surface,he notes that the intensity of light coming from a distance $X$ from his building is the least,and this corresponds to the light coming from light bulbs at height $Y$ on the tower. The values of $X$ and $Y$ are respectively close to (refractive index of water $\simeq \frac{4}{3}$)

Critical angle for a certain medium is $\sin ^{-1}(0.6)$. The polarizing angle of that medium is

$A$ beam of light $AO$ is incident on a glass slab $(\mu = 1.54)$ in a direction as shown in the figure. The reflected ray $OB$ is passed through a Nicol prism. On viewing through the rotating Nicol prism,we find that $(\tan 57^{\circ} = 1.54)$.

For a given medium, the polarizing angle is $60^o$. What will be the critical angle for this medium?