If you have an unpolarized radiation from a broadband light/thermal source propagating through a medium packed with spheres (inter-sphere distance less than wavelength), do you need to account for coherent interactions (i.e., "dependent scattering") using Maxwell's equations?

One approach to conceptualizing broadband radiation is to consider a collection of monochromatic sources - in this conceptualization, reflected waves can interfere with themselves, but other coherent interactions require same relative phase and polarization in their waves. For a thermal source, there is no guarantee for a constant relative phase, and waves scattered from constituent spheres experience change in polarization. It seems then that coherent interactions are not so important and radiative transfer can be modeled with the scalar radiative transfer equation (Boltzmann transport equation) where only intensities are added. Yet there are many theories like "dense medium radiative transfer" and "analytic wave theory" which I think seem to be applied in instances of incoherent light. What am I missing?


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