$A$ point source of light is placed $4 \; m$ below the surface of water of refractive index $5/3$. The minimum diameter of a disc which should be placed over the source on the surface of water to cut-off all light coming out of water is ... $m$.

The critical angle of light going from medium $x$ to medium $y$ is $\theta$. The speed of light in medium $x$ is $v$. The speed of light in medium $y$ is:

What will be the minimum angle of incidence $i$ such that total internal reflection takes place at both interfaces (in $^{\circ}$)? (Given: $\mu_1 = \sqrt{2}, \mu_2 = 2, \mu_3 = \sqrt{3}$)

In the given figure,at the water-air interface,a light ray is incident at the critical angle. Find the value of $\mu_g$.

The critical angle for a monochromatic light going from medium $A$ to medium $B$ is $\theta$. If the speed of light in medium $A$ is $V$, then the speed of light in medium $B$ is

$A$ ray of light travelling in a transparent medium falls on a surface separating the medium from air at an angle of incidence of $45^\circ$. The ray undergoes total internal reflection. If $n$ is the refractive index of the medium with respect to air,select the possible value$(s)$ of $n$ from the following: