The effect of polydispersity on the total integrated intensity and spectral density of light scattered by linear polymers in dilute solution is studied. Use is made of the chain model with nearest- and next-nearest-neighbour linear interactions. The length distribution is chosen to be that of Schulz. The analysis proceeds via normal mode decomposition, and the centre of mass contribution to the spectral density—as well as that of the normal modes, with and without mixing—becomes visible. The influence of polydispersity and elastic constants is significantly manifested in the normal mode contributions, and the spectral density curves of the polydisperse system are narrower than those of the monodisperse case.