Physics
Light houses are places with powerful lights to :

Guide and warn the ships coming from different directions in the ocean
Indicate to the incoming warships, the location of a harbour during night
Guide and resolve traffic jams in crowded metro-cities during nights
Guide and help large crowds at religious gathering during nights

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

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