Why do electromagnetic waves oscillate?

[scottwallace]

Hi everyone,

I have a specific question regarding the nature of electromagnetic waves. I understand he basics of EM waves (frequency, amplitude, wavelength, etc.) and that 'it' is a pair of oscillating fields; one electric and one magnetic, perpendicular to the direction of travel.

What I want to understand is, *what* exactly is oscillating?

I know that all EM radiation is composed of photons... but are the photons themselves traveling a sinusoidal path through space? I suspect not. Is the EM wave pattern simply the total sum of the probabilities of the location of the photons at any given moment?

I am hoping someone can help answer this question for me (and that I've asked it correctly!).

 

[Drakkith]

The Photon IS the wave. More specifically, the energy of a photon propegates AS a wave with oscillating fields. The photon isn't a little ball that travels through space which simply acts like a wave because we can't find the particle.

I believe the FAQ in the general physics forum has more info on this.

 

[scottwallace]

The Photon IS the wave. More specifically, the energy of a photon propegates AS a wave with oscillating fields. The photon isn't a little ball that travels through space which simply acts like a wave because we can't find the particle.

Ok, so I worded the question badly. ;)

I'm trying to determine what the "oscillating fields" are made of. How is the energy stored in those waves? What comprises those fields? (Again, sorry if I'm just not 'getting it')

I believe the FAQ in the general physics forum has more info on this.

Thanks, I'll check it out.

 

[Studiot]

Hello ScottWallace, that is a very good question (yes you asked it quite correctly) that occupied the minds of some of the greatest physicists for centuries.

There was once a proposal that the oscillating 'substance' was called the Lumeniferous Aether and the (unsuccessful) search for it lead to the Theory of Relativity.

To try to answer your question I will concentrate on the electric field.

What do we mean by an electric field?
Well it is a zone of space where susceptible objects willl be influenced by it. That is they will experience a force. This is similar to the gravitational field.

Now we know that the potential energy of an object in a gravitational field depends upon its position (height above surface). We can also say that the 'gravitational potential' at any point is some specific value. This potential has the same value, regardless of the object that is placed at that point. The potential energy is the value of the 'potential' multiplied by the mass.

We can do a similar thing with an electric field. We say that there is an 'electric potentia'l at any point. The potential energy of a charge is the potential multiplied by the charge.

Now the big difference is that, so far as we know, gravity does not oscillate ( gravity waves have been postulated) but the electric potential can indeed oscillate.

Now neither potential' needs a medium they both function perfectly well in a vacuum.

We can develop a similar argument for a magnetic potential.

So the wave is an oscillatory disturbance in the potential of the electric field.

Hope this helps.