Physics
What is a compound microscope?

A microscope whose lenses are convex.
A microscope that has two sets of lenses : an occular lens and an eyepiece.
A microscope that has one lens.
A microscope whose lenses are concave.

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Physics
Light houses are places with powerful lights to :

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

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