__________ is the process of returning the atoms eventually from the higher state to the ground state by emitting their excess energy

The lasers are classified

_________ is the process of stimulating an atom in the higher energy state to make a transition to the lower state with the creation of a second photon due to the interaction of photons of energy E

__________ is the process of increasing population in the upper energy level so that it is greater than the lower energy level, to achieve the laser action.

Different methods used to achieve population inversion are

The population inversion takes place at __________ medium.

In Stimulated Absorption, what is the lifetime of atoms ground state?

The energy of photon is equal to

To obtain laser output properly, rate of __________ of radiation must dominate the __________ radiations.

Einstein's coefficient $B_{12}$ stands for