Physics
The reflector of a search light is a :

Plane mirror
Concave mirror
Cylindrical mirror
Convex mirror

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Physics
Why two thin shirts can keep us warmer than a single thick shirt in winter ?

Air layer between two shirts works as good conductor
Two thin shirts become thicker so prevent transmission of heat
No radiation of heat takes place
Air layer between two shirts behaves like insulating media

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

Metals are good conductors of heat
Plastics have a lower density than metals
Metals have higher thermal capacity than plastics
Plastics have a higher thermal conductivity than metals

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