The phenomenon by which light travels in an optical fibre is

$A$ beam of light consists of red,green,and blue colors. It is incident on the $AB$ face of a right-angled prism as shown in the figure. The refractive indices for red,green,and blue colors are $1.39$,$1.44$,and $1.47$ respectively. What will a person see when looking at the $AC$ surface of the prism?

The refractive indices of the material of the prism and the liquid are $1.56$ and $1.32$ respectively. Find the value of $\theta$ for total internal reflection at the interface.

Initially,$AB$ is the interface of a slab of refractive index $\mu$ and air. $A$ ray of light strikes $AB$ at the critical angle $\theta_c$. Now,a slab $ABCD$ of refractive index $\mu_1$ is placed on top such that total internal reflection takes place at the surface $CD$ (and not at the surface $AB$). What should be the value of $\mu_1$?

For a light ray to undergo total internal reflection, light must travel from $(i = \text{angle of incidence}, i_C = \text{critical angle})$

Explain internal reflection and total internal reflection.