# Photons and magnetism

1. Feb 7, 2012

### 2sin54

At first, I want to say that electromagnetism is my weakest physics branch so this question might sound silly.

Electromagnetism unified electricity with magnetism and the quanta of electromagnetic force is a photon. Is there any link between magnets and photons? Is there any link between electricity and photons? I mean do photons play any kind of a role in magnetism or electricity? I ask these questions because as far as I know, only electrons are responsible for these things.

2. Feb 7, 2012

Anyone?

3. Feb 7, 2012

### Skaperen

Consider a radio transmitter fed antenna. Electron movement creates the magnetic field. Back and forth (or change) causes it to propagate outwards in waves. These are equivalent to photons (two ways to look at the same thing). People often think of light as photons. But radio waves are just a longer wavelength due to a lower frequency. They still have to be photons, too. You can do the double slit experiment at radio wavelengths, but the slits need to be larger and further apart. I'm still looking for the elegancy of this, and am convinced it is there, hiding from me.

4. Feb 8, 2012

### 2sin54

Alright, so the magnetic field itself is made of photons. Thank you.

5. Feb 8, 2012

### Drakkith

Staff Emeritus
Hmm. The photon is the carrier of the EM force, but I don't know if it's correct to say the field is "made" of photons.

6. Feb 9, 2012

### 2sin54

But the field has to contain something, hasn't it?

7. Feb 9, 2012

### Subductionzon

Not really. A photon is a "particle" but when you get down to the quantum level you cannot think of a particle as you would a piece of dust for example. To describe it correctly it had to be done in mathematical terms only. You cannot even locate a photon exactly. The lower energy it is the larger the area that it could "be" is. If you want to think of a photon as something you might try to imagine it as a traveling probability packet. You can calculate where the center of that probability packet is but the photon can "hit" objects outside of that center. And again, the lower the energy is, the wider the area is that it can hit. That is why a bridge which you can see through will block quite a bit of an AM radio signal. The big fat probability packets hit the steel girders and are absorbed. The higher energy FM signal has too small of a packet and most of them make it through. Light waves are higher energy yet and they will travel in what your eyes see as a straight line. The size of their probability packet would be very small.

This is rather laymanish and therefore wrong. But it might help you to understand the concept of a photon.

8. Feb 9, 2012

### 2sin54

So is it right to say that the field contains photons and we need to treat photons in this field as waves?

9. Feb 9, 2012

### Dickfore

waves, as the ones emitted from an antenna, are best described by what is called a coherent state. In it, the number of photons is not known exactly.

10. Feb 9, 2012

### Drakkith

Staff Emeritus
I think you should make a new post in the Quantum Physics forum. That would be the best place for what you are asking.

11. Jul 4, 2012

### Zentrails

No, only if that field is actually applying a force to something.
If a force is applied to something due to an E or M field, then there are photons involved (sometimes called "virtual" photons which is fudging a bit, IMO).
The measured force is explained as an example of conservation of momentum.

i.e. there's no "spooky action at a distance."

http://www.levitationfun.com/mfield.pdf
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