Derive Relation between Einstein`s Coefficients A & B in LASER. Relation between Einstein`s Coefficients A & B Let us consider an atomic system in thermal equilibrium at absolute temperature T. Let N1 and N2 be the number of atoms per unit volume in the ground energy state E1 and excited energy state E2 respectively. Let Ju is the energy density of the incident … [Read more...] about Relation between Einstein`s Coefficients A and B