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.
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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