What generates black-body photons?

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Discussion Overview

The discussion centers around the generation of black-body photons, specifically how these photons are produced in the context of thermal radiation. Participants explore the mechanisms behind black-body radiation, comparing it to spectral photon generation and discussing the complexities involved in bulk materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that black-body radiation is thermal radiation and seeks clarification on the generation of these photons.
  • Another participant suggests that black-body photons are generated similarly to spectral photons, where electrical charges move to lower energy states, but with more complexity in bulk materials.
  • A further explanation indicates that energy absorbed by a black body is quickly spread out among various internal degrees of freedom, leading to the emission of black-body radiation.
  • It is proposed that the transitions responsible for black-body radiation may involve whole atoms or molecules, rather than just single electrons.
  • One participant mentions that vibrational modes may require multiple atoms, and that phonons can represent macroscopic motions within a crystal structure.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding and agreement on the mechanisms of black-body radiation, with some proposing similar principles to spectral photon generation while others highlight the complexity and involvement of multiple atomic or molecular interactions. The discussion does not reach a consensus on the specifics of these mechanisms.

Contextual Notes

Participants acknowledge the complexity of energy states and transitions in black bodies, noting that the discussion involves assumptions about the nature of energy distribution and the types of interactions that lead to photon emission.

persab
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TL;DR
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?
 
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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.
 
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persab said:
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.
 
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Dale said:
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.
 
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PeterDonis said:
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.
 
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Thx all, very helpful!
This is an awesome forum!
 
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