What Does Laser Stand For? Describe Four Different Applications, Clearly Stating Their Principle?

            It stands for "light amplification by stimulated emission of radiation". I t is device that generates "well organized" or "coherent" light. Its beam is composed of photons which have the same wave length, & move in a step like a well drilled army.

            Principle of laser: A photon emitted from an atom induces an electron in another excited atom to fall immediately to a lower level and emits a photon identical to it. Thus stimulated emission can be used to increase the number of emitted photons. Energy is first pumped into a laser medium (ruby rod/CO 2) by a flash lamp. It raises the electrons just above the ground level. Initially only few atoms radiate photons simultaneously. Two silvered end mirrors, one partially transparent reflect the radiation back and forth repeatedly, inducing a chain reaction of photon emission. All the electrons return to ground state simultaneously and a powerful pulse of laser light emerges from a partially transparent end.

            Applications of laser; dentists use laser to remove decay from tooth. Laser can be focused very accurately on a point, this can cut steel and surgeons can use that laser knife in very delicate operations. In eye-surgery, the detached retina can be welded back into place by a laser beam. Laser produces three dimensional images called as "holography".

LASER is Light Amplification of Stimulated Emission of Radiation. And it has many applications. Search for it in google ^_^