The Lorentz–Maxwell model of dispersion of light has been analysed in this paper to determine the damping coefficient of the electrons in optically transparent glasses at the true resonance frequency in the ultraviolet region where glass is opaque. For this, we needed the refractive indices of glass in the optical frequency range. We argue that the true resonance condition in the absorption region prevails when the frequency at which the absorption coefficient is maximum is the same as the frequency at which the average energy per cycle of the electrons isalso a maximum. We have simultaneously solved the two equations obtained from the two maxima conditions numerically to arrive at a unique solution for the true resonance frequency and the damping coefficient at this frequency. Assuming the damping coefficient to be constant over a small frequency range in the absorption region, we have determined the frequency at which the extinction coefficient is maximum using our theory. This frequency matches well with the published experimental data for silica glasses.