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Optical fibres and refraction
Transcript of Optical fibres and refraction
To know how optical fibres work
To know how refraction happens
To know the laws of reflection
All light waves, which hit the surface beyond this critical angle, are effectively trapped. The critical angle for most glass is about 42 °.
An optical fibre is a thin rod of high-quality glass. Very little light is absorbed by the glass. Light getting in at one end undergoes repeated total internal reflection, even when the fibre is bent, and emerges at the other end.
Law of reflection
When light ray strikes a pl____ m____r, the a______ of i______ is e_____ to the ________ of _________.
Waves going from a dense medium to a less dense medium speed up at the boundary. This causes light rays to bend when they pass from glass to air at an angle other than 90º. This is refraction.
Beyond a certain angle, called the critical angle, all the waves reflect back into the glass. We say that they are totally internally reflected.
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Uses of optical fibres
See page 323