In this final chapter of Part III, thermal radiation will be studied from various perspectives that go beyond the uniform systems view taken in Chapter 7. The treatment offered here will not be a complete continuum model; rather, we will take a closer look at some aspects that make radiation unique among the heat transfer modes. Certain forms of distributions of radiation need careful consideration. First, we need to take a look at the angular distribution of radiation in space (Section 12.1), then the spatial tral distribution and polarization will be discussed in detail (Section 12.3 and Section 12.4). Applications of radiative transfer–essentially in the field of solar energy engineering– will be treated in Chapter 16.