# What composes the E Field of the Electromagnetic Wave where "disturbances" for propagation occurs? [duplicate]

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?

You are confused about electromagnetism. The thing is, there generaly (if we leave quantum mechanics out of it) is only electromagnetism, which can manifest itself as magnetic field, electric field, or usualy electromagnetic field depending on the reference frame you're observing it from.

What you need to know is that moving electric charges create a magnetic field that is propagating away from the charges at the speed of light.

Static electric charges create an electric field that is propagating away from them at the speed of light.

A changing magnetic field (accelerating charges) create an electric field around them.

Photons don't interact with electric field (under normal circumstances). They interact with charged particles like protons or electrons by exerting force on them.

You can Picture empty space as a space where there are many different fields which are 0 on average. When a photon, which is just an excitation in the electromagnetic field travels trough that space it is a wave of electrical and magnetic potential that is traveling trough the empty space. When it's at a certain point it increases a value of electric field in that point. Which you can actually measure. Now if you would to put an electron in that same location, the electric field (caused by photons) would interact with it, pushing it in some direction.

• So you're saying a Field is "nothing" but a representation of what we observe. Because if there are no interactions with any matter (emptiness), then it is basically only a traveling photon. I'm confused about the E Field because it increases and decreases in magnitude due to disturbances, and I'm not seeing what is "in" in that magnitude. No explanation.
– Rain
Commented Feb 10, 2017 at 11:28
• Another question - In air, at radio/microwave frequencies, I was told by a physicist in university that they do not interact at all with the electrons in the air because they are bonded and the Photons at this regime are too low in energy. So, basically, a wave propagates with no electron interaction or any other interaction. Just nothingness and travelling photons?
– Rain
Commented Feb 10, 2017 at 11:31
• Quantum mechanics explains why this is so. Bassicaly electrons are only stable at certain energy levels. So if a photon doesn't have a higher energy than that, it doesn't interact with it. But a more accurate Picture would probably be that instead of thinking about a photon, you think of a moving electromagnetic field. The photon interacts with every atom, accelerating them. The atoms shake with their own frequency depending on the medium they're in. This creates it's own electromagnetic field that is then traveling on. But because it lags behind the original field....... Commented Feb 10, 2017 at 11:38
• it adds up with the original wave in such a way that it partialy reduces it's value. When this happens, we could observe that the front of the wave is actualy being reduced to 0. Which we could then interpret as light slowing down, when it's actualy always traveling at the speed of light, just that the interaction with the medium act's to counter it's fron wave. We get the illusion of light traveling slower. Commented Feb 10, 2017 at 11:40
• Thank you. It's become clearer in regards to electrons. I have other photon interaction questions, but will post as a different question to not confuse the readers. You were very helpful.
– Rain
Commented Feb 10, 2017 at 12:02