Polarization of Light: 2 Degrees & Longitudinal Electric Field

[captain]

I have question about the two degrees of polarization of light. I know for a fact that light has only two degrees of polarization for a fact, which just means that light is transverse, but i want to understand what does the longitudinal electric field that you get from a columb field mean really. I have been told there are no degrees of freedom associated with it but i am still not clear. I have also heard that electric and magnetic fields are made up of photons but this static electric field doesn't seem to be made up of photons since its longitudinal and photons don't have three degrees of polarization. What does this mean? Also if you have moving particle, you can boost to frame in which it's stationary and from that rest frame it will look as though the particle emits a static electric field with no magnetic field. If someone could really clarify all of these misconceptions that would be much appreciated. Thanks in advance.

Edit: I am not sure if this is supposed to go in quantum or classical. I am guessing that its quantum.

 

[RedX]

that's a good question and I'm not quite sure I know the answer.

far from any charges, light, which is the electromagnetic field, has only two polarizations - nothing quantum about this, this is what Maxwell's eqns. say.

when charges are brought forth, the electromagnetic field is different, there are fields that don't propagate like light. light in free-space obeys a differential equation that tells you how it varies in space, independent of any charges.

that this additional non-light electromagnetic field has zero degrees of freedom means that it's uniquely determined by specifying how the charges are moving. light does not have this uniqueness, because then you say there is no charges at all, but the electromagnetic field is not specified - you can have light here, or there, or over there, etc.

add: you can always add the solutions of light in empty space to space where there are charges.. in differential equation-speak, there are infinitely many homogeneous solutions, but one particular solution, and this particular solution is the zero degrees of freedom that result from adding the charges which makes it nonhomogeneous. Or something like that.

 

[Entropia]

Hello,

I can understand your confusion about the two degrees of polarization of light and the concept of a longitudinal electric field. First, let me clarify that light does have more than two degrees of polarization. In fact, there are infinite possible polarizations for light, but it is often simplified to two main types: linear and circular. This is because most light sources produce light that is predominantly linearly or circularly polarized.

Now, onto the concept of a longitudinal electric field. This refers to an electric field that is oriented in the same direction as the direction of propagation of the light wave. In contrast, a transverse electric field is perpendicular to the direction of propagation. In a classical electromagnetic wave, both electric and magnetic fields are transverse and perpendicular to each other. However, in some cases, such as when considering the electric field of a single charged particle, the electric field can be longitudinal.

You are correct in saying that there are no degrees of freedom associated with a longitudinal electric field. This is because it cannot be polarized in different directions like a transverse electric field can. As for your question about photons, it is true that both electric and magnetic fields are made up of photons. However, a static electric field does not involve the emission or absorption of photons. Rather, it is a result of the interaction between charged particles.

In regards to your last point about a moving particle appearing to emit a static electric field in its rest frame, this is a consequence of relativity. In the rest frame of the particle, the electric field appears to be static because the particle is not moving. However, in a different frame of reference, the electric field will appear to be changing due to the particle's motion.

I hope this helps to clarify some of your misconceptions. If you have any further questions, please don't hesitate to ask. Science can be complex and it's important to continue asking questions and seeking understanding.