Physics
To measure the speed of an approaching car a police officer shines

Radio waves on it
Ultra high frequency waves on it
Microwaves on it
Light waves on it

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Physics
On a cold day when a room temperature is 15oC, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15oC, because

plastics have a lower density than metals
plastics have a higher thermal conductivity than metals
metals have higher thermal capacity than plastics
metals are good conductor of heat

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