Mechanism of reflection at the atomic scale

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Discussion Overview

The discussion revolves around the mechanisms of reflection and emission of metals, particularly in the context of their interaction with sunlight. Participants explore the differences between these processes at the atomic scale, addressing both theoretical and conceptual aspects.

Discussion Character

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

Main Points Raised

  • One participant questions the difference between reflection and emission, noting that emission involves an electron being excited by a photon and then emitting photons upon de-excitation.
  • Another participant asserts that reflection does not occur at the atomic scale due to the larger wavelengths of optical light compared to atomic dimensions, suggesting that scattering and ionization are more relevant phenomena.
  • A claim is made that metals reflect because they are conductors, prompting further inquiry into the reasons behind this property.
  • Reflection is described as involving the polarizability of a material, where a small perturbation of the electron cloud occurs rather than a transition to a different orbital shape.
  • A participant challenges the notion that reflection cannot be discussed at the atomic scale, suggesting that different types of reflection (specular, diffuse, scattering) could be analogous to celestial bodies, and that the original question remains valid.
  • It is noted that the reasons conductors reflect are detailed in classical electrodynamics textbooks, implying a more complex explanation exists.

Areas of Agreement / Disagreement

Participants express disagreement regarding the validity of discussing reflection at the atomic scale, with some asserting it is not applicable while others argue for its relevance. There is no consensus on the mechanisms of reflection versus emission at this scale.

Contextual Notes

Some statements rely on definitions that may not universally apply, and the discussion includes unresolved questions about the nature of reflection and emission processes at the atomic level.

tom421421
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Hi,

I'm currently looking into reflectivity and emissivity of metals in sunlight. However, I can't quite grasp how the mechanisms of reflection and emission differ. Emission obviously occurs because an electron is exited by a photon and then is de-excited and emits photon or photons. However I don't see how reflection is different when looked at on the atomic scale?

Anyway if anyone has an explanation please let me know!

Cheers
 
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Reflection doesn't happen at the atomic scale. Optical light has wavelengths much much larger than an atom. For radiation that is down close to the atomic scale you typically get scattering and ionization, not reflection. It doesn't make sense to me to talk about reflection at the atomic scale because for reflection to occur you need a smooth surface and no surface is smooth at the atomic scale.
 
metals reflect because they are conductors
 
granpa said:
metals reflect because they are conductors
Why do conductors reflect?
 
tom421421 said:
Emission obviously occurs because an electron is exited by a photon and then is de-excited and emits photon or photons. However I don't see how reflection is different when looked at on the atomic scale?
Transitions between quantum stationary states are not the only kind of emission that is possible (consider the continuous spectra of reflections and black body radiation, versus the quantised "atomic" lines). Reflection has to do with polarisability of a material; at the atomic scale it involves a small perturbation of the electron cloud rather than a jump to a completely different orbital shape.

DaleSpam said:
Reflection doesn't happen at the atomic scale.
Would you say that specular reflection, diffuse reflection and scattering are like planets, planetoids and asteroids? (In other words, I think your absolute statement is just defining your terms rather than describing a physical process. Even considering reflection as some emergent/aggregate phenomena, isn't the OP still valid in asking what is going on down to the atomic level within a larger piece of material?)

Artlav said:
Why do conductors reflect?
That is answered in detail in (classical) electrodynamics textbooks.
 
Last edited:

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