Light enters at an angle of incidence in a transparent rod of refractive index n. For what value of the refractive index of the material of the rod, will the light, once entered into it, not leave it through its lateral face whatsoever be the value of the angle of incidence?
1. $n$ $>\sqrt{2}$
2. 1.0
3. 1.3
4. 1.4

A rainbow is formed due to:

A disc is placed on the surface of a pond which has a refractive index of $\frac{5}{3}$. A source of light is placed 4 m below the surface of the liquid. Find The minimum radius of a disc so that light does not come out from it.
1.  ∞
2.  3 m
3.  6 m
4.  4 m

Optical fibre is based on:
1. Total internal reflection
2. Less scattering
3. Refraction
4. Less absorption coefficient

For the given incident ray as shown in the figure, in the condition of the total internal reflection of this ray, the minimum refractive index of the prism will be:

1. $\frac{\sqrt{3}+1}{2}$

2. $\frac{\sqrt{2}+1}{2}$

3. $\sqrt{\frac{3}{2}}$

4. $\sqrt{\frac{7}{6}}$