Question about electromagnetism and photons

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Discussion Overview

The discussion revolves around the differences between electromagnetic (EM) radiation (photons) and EM fields, particularly in the context of antennas emitting signals. Participants explore the nature of EM radiation, the relationship between frequency and photon emission, and the implications of quantization in low-power scenarios.

Discussion Character

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

Main Points Raised

  • Some participants inquire about the distinction between EM radiation and EM fields, suggesting that EM radiation consists of oscillating electric and magnetic fields.
  • There is a proposal that when an antenna emits a signal at a certain frequency, it produces both photons and oscillating fields, with the frequency of the emitted photons corresponding to the frequency of the EM field oscillation.
  • One participant asserts that if an antenna's signal has a wavelength of 600nm, it would produce visible light, specifically identifying it as orange.
  • A question is raised about the quantization of EM fields, particularly whether low power emission affects the validity of the "Received Power is proportional to the inverse of the square distance" principle.
  • Another participant responds by stating that photons also dilute as 1/r^2 and that quantization leads to more sporadic signals but does not alter the time-averaged power received.

Areas of Agreement / Disagreement

Participants express differing views on the implications of quantization and the relationship between emitted photons and EM fields. There is no consensus on the effects of low power emissions on established principles of EM radiation.

Contextual Notes

The discussion includes assumptions about the nature of EM fields and radiation, as well as the conditions under which certain principles apply. The relationship between power, distance, and quantization remains unresolved.

hcs
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Sorry if this has been asked before, I searched but didn't find anything

What's the difference between EM radiation (photons) and EM fields? When an antenna is emitting a signal at X Hz, is it emitting photons with the frequency of X Hz or is it just making electrical and magnetical fields (and thus called EM)

If my antenna's signal had a wavelength of 600nm (out aside the technological difficulties), would it produce visible light?


Thanks
 
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hcs said:
What's the difference between EM radiation (photons) and EM fields?

EM radiation can be said to be oscillating electric and magnetic fields.


When an antenna is emitting a signal at X Hz, is it emitting photons with the frequency of X Hz or is it just making electrical and magnetical fields (and thus called EM)

Both, actually. Photons are the particle manifestation of light (light acts like both particles and a wave). But to clarify, when I say it produces photons of that frequency, I don't mean the frequency with which it emits photons, I mean the frequency of the EM field oscillation.

Which it behaves like (particle or wave) depends on the context.


If my antenna's signal had a wavelength of 600nm, would it produce visible light?

Yeah, that's orange, I believe.
 
So that means that even EM fields are quantized? By this I mean to ask if the system is emitting so little power that only emits a few photons, the "Received Power is proportional to the inverse of the square distance" is no longer true?
 
hcs said:
So that means that even EM fields are quantized? By this I mean to ask if the system is emitting so little power that only emits a few photons, the "Received Power is proportional to the inverse of the square distance" is no longer true?

Photons dilute as 1/r^2 as well. The fact that it's quantized will make the signal more sporadic, but it won't change the time-averaged power that's received. This happens a lot in high-energy detectors (for X-rays and such) because there are many fewer photons per unit of energy in X-radiation ([tex]E=h\nu[/tex]).
 

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