How laser work??
Laser is a device which produces a highly concentrated monochromatic, coherent and unidirectional beam of light. The way it does is easy if we understand few simple things: Induced absorption: We know that the electrons takes discrete energy level to change their orbits. The source of that energy can be alot of things. Photon is one of them. The energy carried by a photon is hf . If a suitable photon of energy hf strikes the electron it absorb it and moves to higher orbit. This absorption is called induced absorption. Einstein postulated that the rate of this absorption is directly proportion to the number of atoms present in ground state and the density of incident radiation. i.e. dNe/dt =Bi Pr Ng where Ne is the n. of atoms in excited state and Ng is the n. of atoms in ground state and Pr is the density of radiations