SKEDSOFT

Substituting the value of N1/N2in Eqn. (1), we get

eq..2 &eq.. 3

comparing eq..2 and 3 we get.

eq..................4 and 5

Relation (4) shows that transition probability of absorption is equal to transition probability of induced emission. Relation (4) has also been proved in semiclassical theory of radiation by using perturbation theory. Equation (5) shows that A₂₁/B₂₁ is proportional to ν³. This is the ratio of Einstein’s
A coefficient of spontaneous emission and Einstein’s B coefficient of induced emission.