Effect of multiple scattering on broadening and the frequency shift of spectral lines

The effect of multiple scattering on the broadening and the shift of the spectral lines of light propagating in a medium is investigated within Wolf's framework. The condition for no blueshift is derived. It is shown that under the same hypothesis the property $\ensuremath{\Delta}{\ensuremath{\omega}}_{N+1}\ensuremath{\gg}{\ensuremath{\delta}}_{N}$ is satisfied. Moreover, the no blueshift condition has been found to be closely related to the no blurring condition. These results might be of relevance in the astronomical domain.