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Laser is the acronym for light amplification by stimulated emission of radiation. Laser light is unidirectional,coherent beam of light. It is also monochromatic (having single wavelength). To understand

When water is heated from 00C to 40C it contracts continously instead of expanding. Conversely expands when cooled down from 40C to 00C . This expansion of water from 40C to 00C is called anomalous expansion.

Friction The surface, if a solid is never perfectly smooth, consequently whenever a body slides over another, there is a sort of resistance to its motion. Hence if two bodies be in contact with each other

A charge can have only electric field or both electric and magnetic fields at the same time, depending upon, it is either at rest or moving with some velocity. The magnetic field can be uniform or nonuniform