Physics
Hot water is poured simultaneously in four metallic tumblers painted outside with different points. After some time the water will be found to have cooled most in the tumbler painted.

Rough white
Shining black
Shining white
Rough black

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Physics
RADAR is used for:

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

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