Does a photon carry a magnetic field?

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Discussion Overview

The discussion revolves around whether photons carry a magnetic field, exploring the nature of photons in relation to electromagnetic fields. Participants examine classical and quantum perspectives, addressing concepts from electromagnetic theory and the quantization of fields.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that photons are quantized excitations of the electromagnetic field, suggesting a connection between photons and magnetic fields.
  • Others argue that photons themselves do not produce magnetic fields, emphasizing that magnetic fields arise from moving charges.
  • A participant notes that while photons are associated with electromagnetic waves, they are not the sources of these fields; rather, the sources are the accelerating charges.
  • There is a discussion about the classical description of light through Maxwell's equations, which depict light as waves rather than particles.
  • Some participants express confusion over the dual nature of light as both waves and particles, questioning the implications of this duality on the understanding of photons.
  • One participant introduces the concept of magnetic monopoles, suggesting that they may play a role in the quantization of magnetic fields, while others clarify that photons are the quanta of the electromagnetic field.
  • There are references to historical perspectives on light, including the corpuscular theory and its evolution into wave theory, with some participants expressing concern over misconceptions about photons.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether photons carry a magnetic field. Multiple competing views are presented, with some asserting that photons are linked to magnetic fields while others maintain that they do not produce them.

Contextual Notes

The discussion highlights the complexity of interpreting electromagnetic theory and the role of photons within it. There are unresolved questions regarding the definitions and implications of terms like "carry" and "quantization," as well as the relationship between classical and quantum descriptions of light.

  • #31
Polyrhythmic said:
The magnetic monopole would play the same role as the electric charge, it would be a source for the magnetic field, not a quantization.

Why would it not be a quantization of the magnetic field, if it is itself, a particle?
 
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  • #32
Goldstone1 said:
Why would it not be a quantization of the magnetic field, if it is itself, a particle?

For the same reason the electron is no quantization of the electric field. I think you're mistaken on what we mean by "quantization of the field". If we look at a traveling electromagnetic wave, quantum mechanically, energy is transferred in discrete packages. Those packages are what we call photons, quanta of the field. The charge would be merely the source.
 
  • #33
Goldstone1 said:
Why would it not be a quantization of the magnetic field, if it is itself, a particle?

But that is not quantization. If you allow for magnetic monopoles, just as we already allow for electric monopoles, then the magnetic field will still be continuous. The quantization of the field means that the energy is quantized. Since a monopole will produce a field of continuous magnitude, there is no quantization of the field.

EDIT: It appears I lost this one by a nose.
 
  • #34
Born2bwire said:
But that is not quantization. If you allow for magnetic monopoles, just as we already allow for electric monopoles, then the magnetic field will still be continuous. The quantization of the field means that the energy is quantized. Since a monopole will produce a field of continuous magnitude, there is no quantization of the field.

EDIT: It appears I lost this one by a nose.

Hah, gotcha! But I still think that a variety of explanations is beneficial, as long as they are not contradictory!
 
  • #35
Born2bwire said:
But that is not quantization. If you allow for magnetic monopoles, just as we already allow for electric monopoles, then the magnetic field will still be continuous. The quantization of the field means that the energy is quantized. Since a monopole will produce a field of continuous magnitude, there is no quantization of the field.

EDIT: It appears I lost this one by a nose.

It's ok, we all make mistakes. :P
 
  • #36
sophiecentaur said:
Before you bring Feynman into a discussion I think you should make sure that you understand just what he did say and didn't say. The 'squiggle' on a Feynman diagram in no way tells us that a particle goes from place to place, for example - can you find any evidence of his actually saying that it does?

There are a million miles between the separate ideas of quanta and particles.

you go me watching his lecture again, I think the 3rd time now :)

He catagorically states "light is particles NOT waves". and shows how experiment demonstrated that using a PM tube. "waves can explain many things, but not light, light is particles"

http://vega.org.uk/video/programme/45"

specifically, if you don't want to sit through the whole lecture... 36mins in and 48mins in


just stirring you up with the... heresy heresy I cry comment ;) but since you asked for a reference from him, I gave it :)

I am NO physicist, just a basic understanding of some things. you could baffle me with maths in an instant. But I will put my trust, on this subject, in some one with a Nobel Prize ;)

cheers
Dave
 
Last edited by a moderator:
  • #37
davenn said:
you go me watching his lecture again, I think the 3rd time now :)

He catagorically states "light is particles NOT waves". and shows how experiment demonstrated that using a PM tube. "waves can explain many things, but not light, light is particles"

http://vega.org.uk/video/programme/45"

specifically, if you don't want to sit through the whole lecture... 36mins in and 48mins in


just stirring you up with the... heresy heresy I cry comment ;) but since you asked for a reference from him, I gave it :)

I am NO physicist, just a basic understanding of some things. you could baffle me with maths in an instant. But I will put my trust, on this subject, in some one with a Nobel Prize ;)

cheers
Dave

But again, the qualifier in the quote that you contested was that classically, light is waves and this is unequivocal in my opinion. The particle behavior of light does not arise unless you go to quantum electrodynamics (although we can certainly see particle behavior using classical experiments but classical theory fails to account for it). But I would even caution against labelling it as a corpuscle as that carries a very classical definition. The quantum field theory particle is not truly corpuscular, it is an amalgamation of what we classically think of as a wave and a particle.
 
Last edited by a moderator:
  • #38
Born2bwire said:
. . . . But I would even caution against labelling it as a corpuscle as that carries a very classical definition. The quantum field theory particle is not truly corpuscular, it is an amalgamation of what we classically think of as a wave and a particle.

Yes. The problem with trying to think in terms of particles in the conventional sense is that they have to have zero extent, for a start. I say that because, would not their 'size' relate, in some way to their wavelength? This would lead to the lowest energy photons (the 'biggest' ) being the size of a mountain or a house, if you extend the implied size of light photons so that seems a non-starter for a good model. So how would these infinitely small particles be expected to interact with the structures they encounter as they would mostly be encountering empty space (analogous to the results of Rutherford scattering)?
To explain how they actually could interact, you'd have to give them some field around them so why not stick with the EM wave to explain it all. The Quantisation aspect need only refer to the energy needed for an interaction to occur and needn't involve these little bullets - except as a useful shorthand, which I agree is useful.
 

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