Through a small window in a furnace, which contains a gas at a high temperature T, the spectral lines emitted by the gas molecules are observed. Because of molecular motions, each spectral line exhibits Doppler broadening. Show that the variation of the relative intensity I(2) with wavelength A in a line is given by me2(-Ao)2 2AT 10) ox exp where m is the molecular mass, c the speed of light, and Ag the mean wavelength of the line.