# Positive and negative light

1. Oct 26, 2014

### k9b4

Is there any difference between light produced by a positive charge and light produced by a negative charge?

2. Oct 26, 2014

### Staff: Mentor

what particles are you thinking of?

3. Oct 26, 2014

### k9b4

If I have an oscillating electron, and an oscillating proton, oscillating at exactly the same frequency, is there any difference between the electromagnetic radiation produced by these charges?

I imagine the electron radiation would repel other electrons, and the proton radiation would repel other protons?

4. Oct 26, 2014

### Staff: Mentor

Is this a homework assignment? If so then what do you think?

5. Oct 26, 2014

### k9b4

This is not a homework assignment.

I think the electron radiation would repel other electrons, and the proton radiation would repel other protons?

6. Oct 26, 2014

### Staff: Mentor

The electromagnetic field generated from the oscillating charges vibrating at the same rate would be the same.

It wouldn't repel other like charges like you're thinking, it's not an electrostatic field.

7. Oct 26, 2014

### k9b4

Why wouldn't it?

Electromagnetic radiation contains an electric field. Electric field causes force on charged particles. Why does the electric field in electromagnetic radiation not repel and attract like other electric fields?

8. Oct 26, 2014

### Staff: Mentor

That's not how EM waves work. EM waves are oscillations of the EM field vectors, meaning that the forces alternates from + to - and back in a direction that is perpendicular to the direction of propagation.

9. Oct 26, 2014

### k9b4

What does this part mean? What force alternates?

10. Oct 26, 2014

### Staff: Mentor

The electric and magnetic forces alternate polarity (directions). If we use arrows to represent the forces, then the arrows will flip from one direction, to the opposite direction, and then back to the original direction once per cycle.

11. Oct 26, 2014

### k9b4

Hmmm okay.

So the only difference between electron light and proton light is the starting force polarity? One will start negative and the other positive?

12. Oct 26, 2014

### Staff: Mentor

I believe that is correct.

13. Oct 26, 2014

### k9b4

Cool thanks for explaining

14. Oct 26, 2014

### sophiecentaur

You could consider a source of EM radiation in terms of a radio transmitting antenna (and everything can scale, if you could get hold of a suitable 'transmitter' for light). The fields produced and the resulting radiated EM waves can be predicted by merely thinking of the currents sloshing up and down in the wire. This current is normally composed of moving electrons but it needn't be; no one worries about that in Antenna Theory. Point is that polarity of the moving charges doesn't have any bearing on the nature of the EM waves produced - it's just a Current. If you wanted to relate the radiated fields to the 'movement' involved, there would just be a 180 degree phase difference for the different polarities of the charge carriers.

15. Oct 26, 2014

### k9b4

To clarify - when the electric field vector points 'upwards', that means that a positive charge at that particular point will experience a force in the upwards direction?

So that means that electron light and proton light originating from exactly the same point and with exactly the same frequency will affect a charge some distance away in exactly the same way - except that the charge being affected will be 'up' for the electron light and 'down' for the proton light (or vice versa)?

Last edited: Oct 26, 2014
16. Oct 26, 2014

### sophiecentaur

You would have no way of knowing what produced the wave, once it's been launched. There is only one kind of E field and H field.
You would be more likely to have success with Positrons in Anti Hydrogen atoms. I wonder if it's been done? Yes - it looks like it has.

17. Oct 26, 2014

### k9b4

But if (theoretically) both charges were in the same spot, and oscillating with the same frequency, their waves would be perfectly out of phase - right?

18. Oct 26, 2014

### sophiecentaur

They would both be modelled as precisely the same Current, but in anti phase, so - yes.