Classically, how can I explain Reflection?

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Discussion Overview

The discussion centers around the classical explanation of reflection, particularly focusing on why metals reflect nearly all visible light compared to glass, and the conditions under which metals become transparent at higher frequencies. Participants explore the interaction of light with electrons in materials, the role of oscillation, and the implications of classical physics versus quantum mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that when a photon interacts with a material, it causes electrons to oscillate, creating a secondary wave that reflects light. They question why this secondary wave in metals is 180° out of phase with the incoming wave.
  • Another participant asserts that the electric field is zero in metals, implying that no electromagnetic wave can propagate through them, raising questions about transparency at high frequencies.
  • A follow-up inquiry asks for clarification on the frequency range relevant to the discussion and references the Drude model for further investigation.
  • One participant challenges the use of photons in a classical explanation, arguing that this leads back to wave behavior and emphasizes that light does not behave like discrete particles.

Areas of Agreement / Disagreement

Participants express differing views on the role of photons in classical explanations and the behavior of metals at high frequencies. There is no consensus on the correctness of the initial claims or the implications of the electric field in metals.

Contextual Notes

Some assumptions about the nature of light and its interaction with materials remain unresolved, particularly regarding the transition from classical to quantum explanations and the specific conditions under which metals may become transparent.

jaumzaum
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Hello guys! I was trying to understand (without involving too much QM) how does reflection works, and why metals reflect almost 100% of visible light while glass does not, and also why when we increase the frequency, metals become transparent.

I know that when any single photon reaches a body, it interacts with all the electrons in the body, and I can explain that in classical physics considering the photon as a wave. The photon makes the electrons oscillate and create a secondary wave in all directions. In metals the frequency of oscillation of these electrons are 180° shifted from the original wave, so forward waves are canceled and 100% of the wave is reflected, by conservation of energy. In other substances, some part of the wave is reflected, some part is refracted, and some part is absorbed.

Ok, this is what I read, and I don't know if it's completely true or well-written. My question is, why metals generate a secondary wave that is 180 ° shifted from the light wave? And why, for higher frequencies, this isn't true?
 
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Electric field is zero in metal. It means no light as EM wave in metal.
 
anuttarasammyak said:
Electric field is zero in metal. It means no light as EM wave in metal.

So why are metals transparent in high frequency waves?
 
Last edited:
jaumzaum said:
I know that when any single photon reaches a body, it interacts with all the electrons in the body
Wait a cotton pickin' second. You wanted a Classical Explanation. Photons don't come into that, however you state it. If you insist on using photons (perhaps you think it is somehow a deeper explanation) then you need to use their wave nature of their probability so you are back with waves anyway.
Little bullets may be a comforting image but light never behaves like little bullets.
 
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