Question

LASER is an acronym for light amplification by
A.Stimulated energetic radiation
B.Spontaneous emission of radiation
C.Stimulated emission of radiation
D.Spontaneous emission of radio waves

Answer 1

Hint:A lot of our technology today depends on LASER like range finding devices, optical communications, barcode scanners, etc. Its name comes from the unique characteristics and working of laser light. We shall analyze the working of laser and expand this acronym to see how it has become so helpful to human life.

Complete answer:
LASER is the acronym for light amplification by stimulated emission of radiation.
To make a laser, all you need to do is give a big collection of atoms enough energy so they are excited and ready to emit light. Once one of them spontaneously emits a photon, it will stimulate some of the others to do the same and you get a nice cascade of illumination. But instead of letting all the light escape, it's more powerful to trap it in between two mirrors and let it bounce back and forth through the atoms. All that passing light will stimulate them to emit even more light and as long as you keep re-exiting the atoms, they keep on emitting light forever.
So once these friendly photons start bouncing around between the mirrors, you can just open up a little whole at one end and then out goes a blinding stream of coherent light – a laser beam.
Therefore, the correct option is (C) Stimulated emission of radiation.

Note:
The question is why does an atom emit light when a photon just passes by! Photons always want to be like other photons, that is, to have the same face, the same polarization and go in the same direction. If a solitary photon passes by an excited atom that could emit another photon, then there is a chance that it will emit one because the two photons want to be together even before the second one exists.