Energy Distribution of EM Radiation ~ One Photon

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Discussion Overview

The discussion revolves around the energy distribution of a single photon in electromagnetic radiation, specifically whether the energy is evenly distributed over a spherical surface or localized at a point upon detection. The conversation touches on concepts from quantum mechanics and the nature of photons in relation to measurement.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Kcodon questions whether the energy of a photon is distributed evenly on a sphere or localized at a point when detected.
  • Warren asserts that a photon is not localized until it interacts with matter, indicating that energy is detected at discrete locations.
  • Kcodon seeks clarification on the probabilistic nature of photons, suggesting a connection to quantum mechanics.
  • Another participant supports the idea that the second option (localization upon detection) is correct, stating that the first option represents an average over many emissions.
  • Claude explains that a photon not yet observed has a spherically symmetric wavefunction, representing a probability distribution, while an observed photon has its energy localized at a point.
  • Kcodon acknowledges Claude's explanation and clarifies that they are referring to the energy observed by a detector, which they agree would be the full energy of the photon.
  • A later reply reinforces that the wavefunction collapses upon detection, leading to particle-like characteristics, referencing the Copenhagen Interpretation of quantum mechanics.

Areas of Agreement / Disagreement

Participants express differing views on the nature of photon energy distribution, with some supporting the idea of localization upon detection and others discussing the probabilistic nature of photons prior to measurement. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

The discussion highlights the complexity of quantum mechanics and the interpretation of photon behavior, with participants referencing different scenarios of observation and measurement without reaching a consensus on the implications.

kcodon
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Hi All,

I've been recently reading a thread, and a question keeps popping up there. Its not very difficult, it just requires a simple yes or no answer...in a single photon emission, is the energy of the photon distributed evenly on the sphere r=ct, or does this sphere represent the probability of the photon being there, and in fact all the energy of the photon is at one point...i.e. a detector would get all of the energy. Ok not quite yes/no but you get the picture.

I believe in the latter, however I would like to know what others think, thus the poll.

Hopefully this will be short and sweet,

Kcodon
 
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The photon cannot be said to be anywhere until it interacts with something. When individual photons interact with matter (like a screen), they always act at discrete locations.

- Warren
 
So you're in favour of probability?

Darn, I should've posted this in QM I think...

Kcodon
 
The second option is obviously correct.
The first is the average result for a large number of emissions.
 
In QM a photon with a spherically symmetric wavefunction, and a similar photon that has been observed are two different scenarios.

By my understanding, for a photon that hasn't been observed, the energy will be distributed symmetrically. The wavefunction that describes the photon represents the probability of the photon being detected at that point.

For a photon that has been observed, the energy will be localised at a point, and as such the detector making the measurement will receive all the photons energy. The wavefunction of the photon in this case is obviously very different to the previous case.

Claude.
 
Thanks again Claude,

Your explanation makes sense - I never considered how under QM they are considered as different events so to speak. I suppose I need to clarify then - I am referring to what energy the detector would observe, and it seems we agree it would get the full energy of the photon.

Kcodon
 
I could've sworn I posted in this thread.

The second one is correct, the 'wave' can be understood as a wave until it is detected, in which the wave function collapses and it retains particle-like characteristics.

Look up: The Copenhagen Interpretation
 

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