Fibre Optics

This is a very important application of total internal reflection. Electromagnetic radiation, this can be light or infra red radiation depending on the application, is shone along a thin glass fibre and as it hits the glass-air boundary at more than the critical angle it reflects along inside the fibre.

Uses of Fibre Optics

In many of the following uses each fibre has an outer cladding of glass and a bundle of the fibres can be enclosed by a plastic cover.
1. Communications – sending information along a light beam. This is useful for telephone, television, radio, computer networks, stereo links, control in aircraft .
2. Endoscopy - seeing down inside a patient's body
3. Illuminating models or road signs using only one bulb
4. Security fencing – very difficult to bypass.

Advantages of fibre optics over copper wire
1. Cheap – glass is made from silica, the basic constituent of sand
2. Light in weight – and so it is useful in aircraft
3. The light beam can carry a huge amount of information because its frequency is so high