Dear all, I needed help in finding a source where the derivation of radiation emitted by a dielectric body is laid out. The derivation of spectral density of radiation emitted from a blackbody at a temperature ##T## is given in many books by populating the energy states using Bose-Einstein statistics. However, try as I might, I have not been able to find any source where the derivation of the spectral density of radiation emitted by a semi-infinite body with a dielectric function ##\varepsilon (\omega)## and at a temperature ##T## is derived from first-principles (populating the quantum states). I'd assume it should be straightforward since the dielectric function can be approximated by Lorentzian harmonic oscillators. Is it not so ? Do you know any book/paper which discusses this in detail ? Many thanks!