An interest thought experiment

[qinglong.1397]

Suppose we have a detector which can detect the electromagnetic wave. If there exists the electromagnetic wave, the detector will flash.

Now, A holds this detector and runs at a constant velocity relative to a charged particle. Will the detector flash? I think it will. In Chapter 11.10 of Classical Electrodynamics by Jackson, we already calculate the electric and magnetic fields in A's frame. The fields are not static. So I think the detector should flash. But the problem is that the fields do not have the wave form. There is no phase term in the mathematical expressions. So, what is the problem?

 

[Andrew Mason]

Suppose we have a detector which can detect the electromagnetic wave. If there exists the electromagnetic wave, the detector will flash.

Now, A holds this detector and runs at a constant velocity relative to a charged particle. Will the detector flash? I think it will. In Chapter 11.10 of Classical Electrodynamics by Jackson, we already calculate the electric and magnetic fields in A's frame. The fields are not static. So I think the detector should flash. But the problem is that the fields do not have the wave form. There is no phase term in the mathematical expressions. So, what is the problem?

A would detect a magnetic field since he will view the (relatively) moving charge as an electric current. This would simply be an application of Ampere's law. He would also be able to detect an induced current if he was carrying a conducting loop connected to a galvanometer. Why do you think he would detect an electromagnetic wave from A?

AM

 

[qinglong.1397]

That is because the electric and magnetic fields are both changing all the time. This is neither a static electric problem nor a static magnetic problem.

 

[Dale]

So, what is the problem?

The problem is simply a poor description of the detector. What does it detect? If just any time varying fields then yes, it triggers. If it only detects fields with "the wave form" then it will not trigger.

 

[qinglong.1397]

The problem is simply a poor description of the detector. What does it detect? If just any time varying fields then yes, it triggers. If it only detects fields with "the wave form" then it will not trigger.

Oh, yeah. Thanks for your reply. I think I should give a clear definition of the detector. Sorry about that.