$A$ 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 $m$)

Consider a glass cube slab of dielectric bound by the planes $x=0, x=a$; $y=0, y=b$; $z=0, z=c$; with $b > a > c$. The slab is placed in air and has a refractive index of $n$. The minimum value for $n$,such that all rays entering the dielectric at $y=0$ reach $y=b$ is

The velocity of light in a medium is half its velocity in air. If a ray of light emerges from such a medium into air,the angle of incidence,at which it will be totally internally reflected,is ......... $^o$

White light is incident on the interface of glass and air as shown in the figure. If green light is just totally internally reflected,then the reflected rays inside the glass contain:

Why is mirage formation seen in deserts during the summer?

$A$ light ray is incident from a medium of refractive index $2$ into a medium of refractive index $\sqrt{3}$. The critical angle is (in $^{\circ}$)