# EM wave generation using a single charge in a vaccum?

• DoobleD
In summary, the conversation discusses the possibility of generating a propagating EM wave by making a single charge oscillate in vacuum. It is noted that in practice, EM waves are typically created by opposite charges oscillating, such as with a dipole antenna. However, it is possible for a single charge to generate an EM wave, as described by the Lienard Wiechert potentials. The conversation also addresses the confusion surrounding the electric field and the radiated field, with the latter being the result of acceleration of charges and the former being an energy store.
DoobleD
I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ?

In practice, when we create EM waves, we (always ?) have opposite charges oscillating, like with a dipole antenna :

In the dipole antenna case, I can see how the fields detach from the antenna when opposite charge oscillate. But if we only have a single charge oscillating in vaccum, is it still possible for the fields to "detach" from the charge ?

When the single charge oscillates, I can picture in my head the E field progressively updating, like waves on ropes (the rope being the E field here). That sounds kind of like an EM wave. But it seems a totally different situation than with a dipole antenna. Here it doesn't seem like the field can "detach" from the charge. Also, I'm not sure the magnitude of the field really varies in space and time here, it seems more like only its direction changes.

I didn't try to calculate anything, not sure where to start for this question. So I'm just trying to picture things in my head, and I realized I don't know how to interpret the field around a single charge oscillating in vaccum. Is it a an wave, is it not really ?

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To my knowledge, this charge will generate an electromagnetic wave. The very definition of an electromagnet is a wave generated by a oscillating charge.

I think you are also confusing many terms. Your question seems very jumbled up and I am finding it difficult to interpret the question.

DoobleD said:
I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ?
Certainly. This is described by the Lienard Wiechert potentials.

DoobleD
DoobleD said:
I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ?
I think your dipole drawings (a) to (d) depict the electric field (electrostatic field) from the charges and not from the radiated field. The latter comes from the acceleration of charges in the conductors and is greatest near the centre. The electrostatic fields are just energy stores and do not propagate away as traveling waves as you depict.

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Thank you for the answers. I'll have a look at Lienard Wiechert potentials.

## 1. How is an EM wave generated using a single charge in a vacuum?

An EM wave is generated when a single charged particle accelerates in a vacuum. This acceleration creates a changing electric field, which in turn creates a changing magnetic field. The changing electric and magnetic fields then propagate through space, creating the EM wave.

## 2. What is the role of a vacuum in EM wave generation using a single charge?

A vacuum is necessary for EM wave generation using a single charge because it allows for the unobstructed propagation of the EM wave. If there were particles or other matter present, they would absorb or scatter the EM wave, preventing it from propagating as a continuous wave.

## 3. Can an EM wave be generated using a single charge in a non-vacuum environment?

Yes, an EM wave can be generated using a single charge in a non-vacuum environment, but the wave will be affected by the presence of other particles or matter. This can result in absorption, scattering, or distortion of the EM wave.

## 4. How does the frequency of an EM wave generated by a single charge in a vacuum relate to the acceleration of the charge?

The frequency of an EM wave generated by a single charge in a vacuum is directly proportional to the acceleration of the charge. This means that as the charge accelerates faster, the frequency of the resulting EM wave will also increase.

## 5. Is it possible to control the direction of an EM wave generated by a single charge in a vacuum?

Yes, the direction of an EM wave generated by a single charge in a vacuum can be controlled by manipulating the direction of the charge's acceleration. By changing the direction of the acceleration, the resulting EM wave will also change direction.

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