Physics
Light houses are places with powerful lights to :

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

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Physics
The velocity of sound in air

Does not depend on temperature
Decreases with increase of temperature
Increases with decrease of temperature
Decreases with decrease of temperature

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Physics
Pressure Cooker cooks faster because

It cooks the food at low pressure
Boiling point decreases with rise of pressure
Higher temperature is attained for cooking
The material of the cooker is a good conductor

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