Physics
A light ray travelling from denser to rarer medium at an angle of incidence more than critical angle of concerned media pair suffers.

Diffraction
Reflection
Refraction
Total internal reflection

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Physics
RADAR is used for:

locating submerged submarines.
locating geostationary satellites.
detecting and locating the position of objects such as Aeroplanes.
receiving a signals in a radio receiver.

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