If the critical angle for total internal reflection from a medium to vacuum is $45^{\circ}$,then the velocity of light in the medium is,

The speed of light in two media $c_1$ and $c_2$ are $1.5 \times 10^8 \ m/s$ and $2 \times 10^8 \ m/s$ respectively. If the light undergoes total internal reflection,the critical angle between the two media is

$A$ point source of light is placed $4 \, cm$ below the surface of water with a refractive index of $\mu = 5/3$. What is the minimum diameter of a disc that should be placed over the source to stop all light from coming out of the water? (in $m$)

As shown,a narrow beam of light is incident onto a semi-circular glass cylinder of radius $R.$ Light can exit the cylinder when the beam is at the centre. When the beam is moved parallel to a distance $d$ from the central line,no light can exit the cylinder from its lower surface. Find the refractive index of the glass.

If the refractive index of water is $\frac{4}{3}$ and that of a given glass slab immersed in it is $\frac{5}{3}$,the value of the critical angle for a ray of light tending to go from glass to water is:

The critical angle for total internal reflection of light going from medium $I$ to medium $II$ is given by the relation $\tan i_C = \frac{5}{9}$. The refractive index of medium $I$ with respect to medium $II$ is: