Question

Define the phenomenon of total internal reflection.

Answer 1

A ray of light travels from optically denser medium to optically rarer medium, it bends away from the normal at the surface separating the two medium.

Complete step by step answer:
When a ray of light passes from denser to rarer medium, its bend away from the normal at the interface of the two media, which is the angle of refraction (r), is greater than the angle of incidence (i).
Critical angel: - on increasing the angle of incidence, the angel of refraction increases and for a particular angle of incidence C (ray) the angel of refraction becomes ${{90}^{\circ }}$ , that is the refracted ray grazes along the interface . This angle of incidence C is called the critical angle for the interface.

Total internal reflection: - When a ray of light travelling from a denser medium to a rarer medium is incident at the interface of the two media at an angle greater than the critical angle for the two media, the ray is totally reflected back into a denser medium. This is called the “Total internal reflection”.

Condition to get total internal reflection: - There are two conditions to occur the total internal reflection.

1. The ray incident on the interface of two media should travel in the denser medium.
2. The angle of incidence should be greater than the critical angle for the two mediums.

Note: For total internal reflection students should learn about the critical angle. Students also remember the direction of rays from one medium to another medium.