Photons emitted by heated objects

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Discussion Overview

The discussion revolves around the emission of photons by heated objects, specifically addressing the mechanisms behind photon emission related to electron transitions and intermolecular forces. It explores concepts from thermal radiation, including Planck's law and the contributions of atomic vibrations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether photons emitted from heated objects are due to electron transitions or if kinetic energy from intermolecular forces is sufficient for photon emission.
  • Another participant states that objects at finite temperatures emit photons according to Planck's law and that contact with a heat bath is necessary to maintain excited states for emission without requiring photons.
  • A different viewpoint suggests that the photons emitted from kinetic energy are not due to electron transitions but rather from oscillating charges within the atoms, which emit photons at their oscillation frequency.
  • One participant acknowledges the original question about photons from electron transitions but notes that other degrees of freedom also contribute to thermal radiation and highlights that real objects do not uniformly populate the energy spectrum, leading to deviations from Planck's law.
  • Further aspects mentioned include the effects of surface roughness, angle dependency of emitted and reflected radiation, and angle-dependent polarization.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms of photon emission, with no consensus reached on whether electron transitions or atomic vibrations are the primary source of emitted photons in heated objects.

Contextual Notes

Participants note limitations such as the non-uniform population of energy states in real objects and the assumptions inherent in Planck's law, as well as the complexities introduced by surface characteristics and radiation reflection.

Amyriel
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Hello everyone,

I have a question. Electrons jumps up the energy level by absorbing a photon and down releasing it, giving off a characteristic spectrum. Then, are the photons released when an object is been heated up due to intermolecular forces, since they are of a full spectrum? Is the kinetic energy of the atoms enough to make the electrons jumps or do they absolutely require a photon?

Thank you :)
 
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An object at finite temperature emits photons according to Planck's law.
See https://en.wikipedia.org/wiki/Black-body_radiation.
If these photons escape the body will cool down to absolute zero unless it is in contact with a heat bath at some temperature. That contact will keep the excited states populated causing the emission, indeed without the need for photons.
 
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The photons created from the kinetic energy of the atoms aren't due to electrons changing energy levels, but simply due to the fact that the atoms are vibrating/oscillating. An oscillating charge will emit photons at a frequency equal to that of the oscillation.
 
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The question was specifically after photons emitted by jumping electrons.
But yes other degrees of freedom of the object also contribute to the thermal radiation.
Also the degrees of freedom of a real object do not populate the energy spectrum uniformly.
This will lead to deviations from Planck's law, which assumes 100% absorption at all wave lengths.
And then there is still reflection of incident radiation to be considered.
Further aspects:
roughness of the surface, which may cause diffuse scattering
angle dependency of emitted and reflected radiation
angle dependent polarization
 
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