Thus stimulated emission at frequencies away from ν ν 0 is reduced by this factor. In practice there may also be broadening of the line shape due to inhomogeneous broadening, most notably due to the Doppler effect resulting from the distribution of velocities in a gas at a certain temperature. This has a Gaussian shape and reduces the peak strength of the line shape function. In a practical problem the full line shape function can be computed through a convolution of the individual line shape functions involved. Therefore, optical amplification will add power to an incident optical field at frequency ν ν at a rate given by P = h ν ν g ( ν ν ) B 21 ρ ρ ( ν ν ) Δ Δ N .