Blackbody aperture radiation: Effect of cavity wall

In this paper we show that the coherence properties of the radiation emanating from an aperture in the single wall of a half-space blackbody cavity can be determined by considering how free-space blackbody radiation is scattered by those apertures. That is, although the presence of the cavity wall modifies the blackbody radiation field, it has no effect on the field components that are relevant in the scattering computations. This conclusion is essential since it justifies the methodology employed in earlier papers. Furthermore, our analysis shows that this computationally simple procedure is rigorous only for the half-space geometry and it also gives indications of when the results obtained by the procedure provide good approximations of the radiated field properties. This work thereby defines the domain of validity of earlier results connected with the coherence properties of blackbody radiation outside the cavity.