$A$ light ray is incident perpendicularly to one face of a $90^{\circ}$ prism and is totally internally reflected at the glass-air interface. If the angle of incidence at the interface is $45^{\circ}$,we conclude that the refractive index $n$ is:

$A$ point source of light is placed at a distance $h$ below the surface of a large deep lake. What is the percentage of light energy that escapes directly from the water surface if the refractive index $\mu$ of the water is $4/3$ (in $\%$)? (Neglect partial reflection)

In the figure,$ABC$ is the cross-section of a right-angled prism and $BCDE$ is the cross-section of a glass slab. The value of $\theta$ so that light incident normally on the face $AB$ does not cross the face $BC$ is (given $\sin^{-1}(3/5) = 37^o$):

Let the refractive index of a denser medium with respect to a rarer medium be $n_{12}$ and its critical angle be $\theta_C$. At an angle of incidence $A$ when light is travelling from a denser medium to a rarer medium,a part of the light is reflected and the rest is refracted,and the angle between the reflected and refracted rays is $90^o$. Angle $A$ is given by

Consider light travelling from a medium $A$ to medium $B$ separated by a plane interface. If the light undergoes total internal reflection during its travel from medium $A$ to $B$ and the speed of light in media $A$ and $B$ are $2.4 \times 10^8 \ m/s$ and $2.7 \times 10^8 \ m/s$ respectively, then the value of critical angle is:

$A$ normally incident ray is reflected at an angle of $90^o$. The value of the critical angle is.......$^o$