If the higher energy state has a greater population than the lower energy state (N 1 < N 2), then the emission process dominates, and light in the system undergoes a net increase in intensity. It is thus clear that to produce a faster rate of stimulated emissions than absorptions, it is required that the ratio of the populations of the two states is such that N 2 / N 1 > 1; In other words, a population inversion is required for laser operation.