Optical fibre is a thin, flexible, transparent strand of glass or plastic used to carry light signals from one place to another, mainly for communication. It works on the principle of total internal reflection.

Class 12 definition

In Class 12 physics, an optical fibre is usually defined as a light- transmitting medium made of a very thin core surrounded by cladding, so that light keeps bouncing inside the core and travels through the fibre.

How it works

  • Light enters the core at an angle.
  • It strikes the core-cladding boundary.
  • Because of total internal reflection, the light stays trapped inside and moves along the fibre.

Main parts

  • Core: the central part that carries light.
  • Cladding: the outer layer with a lower refractive index.
  • Coating: a protective outer covering.

Uses

  • Internet and telephone communication.
  • Cable TV signals.
  • Medical endoscopy.
  • Data transmission over long distances.

One-line exam answer

Optical fibre is a glass or plastic fibre that transmits light by total internal reflection.

Meta description: Optical fibre in Class 12 physics is a thin transparent medium that carries light by total internal reflection, with core, cladding, and coating.