Physics
Light houses are places with powerful lights to :

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

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Physics
Why does the sea appear blue in colour?

Interference of the sun light from water surface
Reflection of the sun light from water surface
Scattering of the sunlight by water molecules
Refraction of the sun light

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