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COMMUNICATION

Wireless Communications
Uses some waves in the electromagnetic spectrum.
Radio waves and some longer wavelength microwaves.
o Other wavelengths are absorbed by the atmosphere.
Atmospheric opacity
o Gamma rays, X rays and almost all UV rays are unable to pass through
the atmosphere. Visible and some wavelengths of infrared…

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Bandwidth
Carrier wave frequency is fc, and the audio information signal is fs.
To avoid interference with signals from other sources, an amount of
spectrum (2fs) must be allotted to the signal, fc.
Most information signals have a range of signals, either side of the carrier
wave.
In FM, there…

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TOTAL INTERNAL REFLECTION

What is total internal reflection?
When going from a low to a high density, you can have any angle of incidence. But,
when going from a high to a low density substance, after a certain angle of incidence
(the critical angle), total internal reflection occurs.
So...
Only…

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Optical fibres
Light is continually totally internally reflected at different points along the glass fibre




Infrared or visible light electromagnetic waves are used. Gamma and X rays
penetrate glass and would escape. UV does not pass through glass.
Microwaves and radio waves have a wavelength that is too long.
The…

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