GCSE Physics

Optical Fibres

Total internal reflection can occur as long as the angles made by the rays are greater than the critical angle.

In glass the critical angle is around 42° and today we use very narrow fibres of glass to transmit pulses of light.

optical fibre showing total internal reflection of a light beam

These are called optical fibres. They are used in telecommunications to transmit telephone conversations and data - including this web page to your computer!

Whilst traditional copper wires can be used (and indeed are for the first 500 m or so from your phone) they cannot carry as much information and suffer from magnetic interference.

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