# Question about electromagnetism and photons

1. Mar 12, 2005

### hcs

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: Mar 12, 2005
2. Mar 12, 2005

### SpaceTiger

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

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.

Yeah, that's orange, I believe.

3. Mar 12, 2005

### hcs

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?

4. Mar 12, 2005

### SpaceTiger

Staff Emeritus
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 ($$E=h\nu$$).