What physical process is the source of blackbody radiation? [duplicate]

Question

Blackbody radiation is the radiation given off an object solely as a result of its absolute temperature. The (continuous) spectrum is given solely by the temperature.

How can this be? Why should a slab of Tungsten at 400 K emit the exact same spectrum as a pile of powdered sodium chloride at the same temperature? Why should the emitted radiation be independent of the chemical composition of the object, the electron transition energies, and the mass of the atomic nuclei?

What is the actual, physical process, that gives rise to the emission of blackbody radiation?

Answer 1

In deriving the blackbody radiation equations, the particular processes of photon radiation don't matter or are not considered into the derivation. The major assumption about the photon radiation is that the photon is in equilibrium with the blackbody at the same temperature so that the photon statistics obey the temperature distribution independent of all various blackbodies (like sodium and tungsten).

If you want to know the detailed physics process of radiation, it really depends on specific objects. When an object is heated up, molecules can vibrate, electrons from a high energy level can spontaneously jump to a lower level to emit a photon, and may got excited to the high level again through molecular collisions or other mechanisms. Other processes may spontaneously happen to emit photons as well for different components of subtracts.

Hope this helps :)