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Lesson: Chapter 5 — Optics

5.3.2. Total internal reflection and the critical angle 3 of 4

Optical fibres

Optical fibres are fine, transparent threads of glass or plastic that carry light along them by total internal reflection.

Light entering one end of an optical fibre and bouncing from side to side along it by total internal reflection until it comes out of the far end.

Light entering a fibre is totally internally reflected again and again along its length, and comes out of the other end. Even if the fibre is several kilometres long, the light comes out almost as bright as it went in.

The endoscope

Doctors examine organs inside the body with an endoscope, which carries light in and the picture out along optical fibres.

Telephone and internet

Optical fibres are now widely used as the cables for telephone communication and internet connections.

Decoration

They are also used in decorative lights.

Figure to be added

An endoscope — a long flexible tube with an eyepiece, carrying light along optical fibres.