I What generates black-body photons?

[persab]

TL;DR Summary

black body radiation

Spectrally generated photons I get: electrons "fall down to a closer orbit" and a photon is created.
I don't understand however how the photons from black body are created. I have searched extensively for this without finding answer.

Can someone enlighten me?

 

[PeterDonis]

Black body radiation is thermal radiation:

https://en.wikipedia.org/wiki/Thermal_radiation

 

[Drakkith]

They are generated in a similar manner to spectral photons. Electrical charges interact and move to lower energy states. The states are just vastly more complicated in a bulk solid or dense gas than in a single atom.

 

[Dale]

Summary:: black body radiation

Spectrally generated photons I get: electrons "fall down to a closer orbit" and a photon is created.
I don't understand however how the photons from black body are created.

It is the same principle. Inside the object there are many different places for a bit of energy to go (internal degrees of freedom). Some are atomic orbitals, some are molecular orbitals, some are linear KE, some are rotational, vibrational, or torsional movements, some are longer range movements, etc. Energy that gets absorbed by the black body gets quickly “thermalized” or spread out amongst all of these degrees of freedom. Black body radiation is just like the orbital transition radiation except there are so many different possible energy levels and degrees of freedom.

 

[PeterDonis]

Black body radiation is just like the orbital transition radiation except there are so many different possible energy levels and degrees of freedom.

It is also worth noting that with black body radiation, the things that make transitions to lower energy states and emit the radiation might not be single electrons; they might be whole atoms or molecules or even larger groupings.

 

[Dale]

It is also worth noting that with black body radiation, the things that make transitions to lower energy states and emit the radiation might not be single electrons; they might be whole atoms or molecules or even larger groupings.

Yes, that is a good point. I am not certain but I think vibrational modes take a minimum of two atoms and torsional modes I think require at least four and many more complex motions can be quite large. Phonons are essentially an entire crystal, basically macroscopic at that point.

 

[persab]

Thx all, very helpful!
This is an awesome forum!