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 emerging ray in air contains:

$A$ ray of light travelling in a transparent medium of refractive index $n$ falls on a surface separating the medium from air at an angle of incidence of $45^{\circ}$. For which of the following values of $n$ can the ray undergo total internal reflection?

$A$ ray of light travelling inside a rectangular glass block of refractive index $\sqrt{2}$ is incident on the glass-air surface at an angle of incidence of $45^{\circ}$. The refractive index of air is $1$. Under these conditions,the ray:

$A$ fish looking from within water sees the outside world through a circular horizon. If the fish is $\sqrt{7} \ cm$ below the surface of water,what will be the radius of the circular horizon in $cm$?

The phenomenon by which light travels in an optical fibre 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 $m$)