Light wave propagation is possible in optical fibre due to a phenomenon called:

Question

Question

This question was previously asked in

ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 1

Answer 1

In an optical fiber, the information is passed through light, which must not escape outside of it.
This phenomenon of confining the light inside the optical fiber is termed as Total internal reflection.
For this, the construction and material used to ensure that the total internal reflection of light takes place to prevent the escape of it.

OFC

Principle:

When light travels from a high refractive index medium to a low-refractive-index medium, it is refracted away from the normal as shown:

ISRO 2014 (1-14) Rishi D6

At a certain angle θi, there is no refracted wave and the wave is totally internally reflected (θr = 90°).
This angle is called a critical angle.
Inside an optical fiber, we have a high refractive index core (n1) and low refractive index cladding (n2).
This results in the propagation of waves inside a fiber through total internal reflection phenomenon.