Question about electromagnetism and photons

AI Thread Summary
The discussion clarifies the distinction between electromagnetic (EM) radiation and EM fields. EM radiation consists of oscillating electric and magnetic fields, and when an antenna emits a signal at a specific frequency (X Hz), it produces both photons at that frequency and oscillating fields. The behavior of light as either a particle or a wave depends on the context. If an antenna emits a signal with a wavelength of 600 nm, it would indeed produce visible light, specifically in the orange spectrum. The conversation also touches on the quantization of EM fields, noting that even with low power emission resulting in fewer photons, the principle that received power diminishes with the square of the distance (1/r^2) remains valid. However, the quantization can lead to a more sporadic signal, particularly evident in high-energy detectors like those used for X-rays.
hcs
Messages
2
Reaction score
0
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
 
Last edited:
Physics news on Phys.org
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 (E=h\nu).
 
Thread 'Motional EMF in Faraday disc, co-rotating magnet axial mean flux'
So here is the motional EMF formula. Now I understand the standard Faraday paradox that an axis symmetric field source (like a speaker motor ring magnet) has a magnetic field that is frame invariant under rotation around axis of symmetry. The field is static whether you rotate the magnet or not. So far so good. What puzzles me is this , there is a term average magnetic flux or "azimuthal mean" , this term describes the average magnetic field through the area swept by the rotating Faraday...
Back
Top