Fibre Optics

When a wave hits an interface between different densities some of it is back while most goes through. There is, however, a critical angle above which all of it reflected back into the more dense medium. For glass into air the critical angle is approx. 43°.

This is called Total Internal Reflection. Light is kept in the fibre optic because every internal incident ray angle is than the critical angle so total internal reflection occurs. Fibre optics are made out of thin continuous strands of covered in an opaque sheath to stop an external light getting in.

Fibre optics can be used for:
• keyhole surgery through the use of endoscopes
• optical fibre Christmas trees and decorative lighting
• long distance Telephone 'cables'
• high speed / high volume data transfer or Internet connection

More information can be carried via an optical fibre than by sending electrical signals through cables of the same diameter. There is also less weakening of the signal in optical fibres, compared to electrical signals so they can be sent .

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