The critical angle for diamond with respect to air is nearly (in $^{\circ}$)

On which principle does an optical fiber work?

In the figure shown,for an angle of incidence $i$ at the top surface,the minimum refractive index $\mu$ needed for total internal reflection at the vertical surface will be

$A$ 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?

$A$ small bulb is placed at the bottom of a tank containing water to a depth of $80 \, cm$. What is the area of the surface of water through which light from the bulb can emerge out? The refractive index of water is $1.33$. (Consider the bulb to be a point source.)

Which of the following is not due to total internal reflection?