What composes the E Field of the Electromagnetic Wave?

In summary: I did not get any new information from your reply. In summary, the conversation discusses the E Field of Electromagnetic Waves and its role in causing disturbances for propagation, as well as the interaction between photons and the E Field. The experts explain that the E Field is a model used to describe the behavior of electromagnetism, and while we do not know the true nature of fields and photons, the model is confirmed through experiments and is therefore accepted. The conversation also touches on the idea of what is considered "real" and where one can start reading on EM field interaction phenomena.
  • #1
ThunderLight
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What composes the E Field of the Electromagnetic Wave where "disturbances" for propagation occurs?

If electromagnetic waves cause disturbances in the Electric Field… what “is” in this E Field which photons Interact with?

I ask because in Vacuum, there are no electrons to excite. So what is “it” that's adding up in the E Field as a disturbance in wave propagation?
 
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  • #2
ThunderLight said:
what “is” in this E Field which photons Interact with?
It's just the E field. That is as deep as the explanation goes. (*) Science is about discovering models that describe how things work. If those models predict measurable results and if experiments match the predictions then that is as good as it gets.

The model you are using describes behavior of electromagnetism in terms of fields. The model can tell you what fields will be produced by a set of charges. It can tell you how charges will respond to a given field. It can tell you how an fields can evolve over time in the absence of charges. When you measure the motion of charges, they match the predictions of the model. So we consider it a good model and move on.

The question of what the fields are made of does not arise. They could be made of little hooks and springs lubricated by fairy dust. The only part that matters to science are the quantitative testable predictions. Until we come up with a way to measure fairy dust, the underlying mechanism, if any, is irrelevant.

(*) You could delve into Quantum Electrodynamics and get a somewhat more nuanced and mind-twisting model, but you still have a bottom level of "that's just the way it works".
 
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  • #3
jbriggs444 said:
(*) You could delve into Quantum Electrodynamics and get a somewhat more nuanced and mind-twisting model, but you still have a bottom level of "that's just the way it works".

That's pretty much what I got from reading some sources on quantum ED. There is no explanation of what a field really is. Or infact, what drives the disturbance, which they say it is the Photon as a Propagator, but others describe the EM fields as the Photons themselves.

Which drove me to asking a lot of questions, and this is just one of them.
And it seems to me - We don't really know what are those fields nor what we called Photons.
Except that Physics only Quantifies these observations.

Thank you for your sincere well written answer.

On another note - Where do I start reading on EM field interaction phenomena... assuming other things than charges cause disturbances or different behaviours in Electric Fields/Magnetic Fields?
 
  • #4
ThunderLight said:
And it seems to me - We don't really know what are those fields nor what we called Photons.

Actually, we know exactly what those fields are because we invented them.
We also know exactly what those waves are because we invented them also.
What we don't exactly know are those photons because those we are only observing.

It's all just different sides of the same thing, energy.
 
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  • #5
Energy, photons, fields -- they are all elements of models. Experiment can only ever tell us whether a model makes accurate predictions. It cannot tell us whether the elements of the model are real. Whatever "real" means.

For models that are well confirmed, we tend to take the existence of the elements of that model for granted. We think of fields, photons and energy as if they were real. As long as experiment does not contradict the correctness of the model, we can go on thinking that way without difficulty.

In the same way we think of people, buildings and Buicks as being real. We each (seem to) have a well confirmed mental model of the world built through childhood which includes those entities and which works well enough to get us through life.

[This response is getting perilously close to being philosophy. It will not break my heart if it is removed]
 
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  • #6
ThunderLight said:
And it seems to me - We don't really know what are those fields nor what we called Photons.

As has been explained already, we know exactly what a field is. A field in this context is a mathematical way of modeling something by having a value at each point in space and time, such as the values describing the electric force felt by a particle at a location. Whether or not this model is "real" or not is mostly a philosophical question. When done correctly, this type of model works accurately and it works beautifully. Therefore it is used extensively in physics and elsewhere (including weather reporting).

Photons are a model of an observed phenomenon; the interaction between matter and the EM field is quantized. This quantized interaction transfers discrete amounts of energy and is called a photon. Again, whether photons "really" exist is a matter philosophy, not physics.

ThunderLight said:
On another note - Where do I start reading on EM field interaction phenomena... assuming other things than charges cause disturbances or different behaviours in Electric Fields/Magnetic Fields?

I don't know what you mean here. As far as I know, electric charges are the only things that generate or cause changes in the EM field.
 
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  • #7
Drakkith said:
As has been explained already, we know exactly what a field is. A field in this context is a mathematical way of modeling something by having a value at each point in space and time, such as the values describing the electric force felt by a particle at a location. Whether or not this model is "real" or not is mostly a philosophical question. When done correctly, this type of model works accurately and it works beautifully. Therefore it is used extensively in physics and elsewhere (including weather reporting).

Photons are a model of an observed phenomenon; the interaction between matter and the EM field is quantized. This quantized interaction transfers discrete amounts of energy and is called a photon. Again, whether photons "really" exist is a matter philosophy, not physics.
I don't know what you mean here. As far as I know, electric charges are the only things that generate or cause changes in the EM field.
Thank you for your answer. Yes, I did mean whether other things than electric charges generate or cause changes in the EM field.
 
  • #8
m k said:
Actually, we know exactly what those fields are because we invented them.
We also know exactly what those waves are because we invented them also.
What we don't exactly know are those photons because those we are only observing.

It's all just different sides of the same thing, energy.

Aha, thank you, it makes more sense now.
 
  • #9
jbriggs444 said:
Energy, photons, fields -- they are all elements of models. Experiment can only ever tell us whether a model makes accurate predictions. It cannot tell us whether the elements of the model are real. Whatever "real" means.

For models that are well confirmed, we tend to take the existence of the elements of that model for granted. We think of fields, photons and energy as if they were real. As long as experiment does not contradict the correctness of the model, we can go on thinking that way without difficulty.

In the same way we think of people, buildings and Buicks as being real. We each (seem to) have a well confirmed mental model of the world built through childhood which includes those entities and which works well enough to get us through life.

[This response is getting perilously close to being philosophy. It will not break my heart if it is removed]

Yes, now I'm beginning to understand it from the concept of models, rather than 'thing'. A quantified model of observations and phenomena.
Thank you.
 

1. What is the E field of an electromagnetic wave?

The E field, or electric field, is one of the two components of an electromagnetic wave. It is a vector field that describes the strength and direction of the electric force at any given point in space.

2. How is the E field created in an electromagnetic wave?

The E field is created by the oscillation of electric charges. In an electromagnetic wave, the changing electric field creates a changing magnetic field, which then creates a changing electric field, and so on, propagating the wave through space.

3. What factors affect the strength of the E field in an electromagnetic wave?

The strength of the E field in an electromagnetic wave is affected by the amplitude of the wave, the distance from the source of the wave, and any intervening materials that the wave travels through.

4. How is the direction of the E field determined in an electromagnetic wave?

The direction of the E field is perpendicular to the direction of propagation of the wave. This means that the E field is always perpendicular to both the electric and magnetic field vectors.

5. How does the E field interact with matter?

The E field can interact with matter in a variety of ways, depending on the properties of the material. For example, in conductors, the E field can induce the flow of electric current, while in insulators, the E field can cause polarization of the material's atoms or molecules.

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