Timeline for How can 2 EM waves null each other at a point but continue to propagate?
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| Apr 3, 2016 at 18:18 | comment | added | Timaeus | @AccidentalFourierTransform If you want to answer it with the linked question you could make it be about all the A and then if A is momentarily zero everywhere you could ask why it isn't gone. But that's just the case when the magnetic field is momentarily gone and the "kinetic" term for A just means there is a nonzero electric field at the moment the magnetic field is gone. The real answer is that two waves can't cancel electrically and magnetically and have opposite momentum. So the situation described doesn't happen. | |
| Apr 3, 2016 at 9:49 | comment | added | AccidentalFourierTransform | @Timaeus I see your point, but I'd say it's 50% a duplicate because it is the same as the other post if we change $y(x,t)\leftrightarrow \boldsymbol E(x,t)$, $\dot y(x,t)\leftrightarrow \boldsymbol B(x,t)$. Or put it another way: Maxwell's equations can always be written as $(\partial_t^2-\nabla^2)A_\mu=0$ for $A_\mu$ the vector potential, so we do have a second order wave equation. EDIT: now I realise this is precisely what your answer below is saying, so we agree there is a resemblance to the other post, right? | |
| Apr 3, 2016 at 2:37 | answer | added | Timaeus | timeline score: 2 | |
| Apr 3, 2016 at 2:13 | comment | added | Timaeus | @AccidentalFourierTransform It's 100% not a duplicate, it's as different as can be. A string has position and velocity as independent parameters because Newton is second order. Whereas Maxwell is first order so knowing the complete values of the electromagnetic field at one snapshot in time tells you what the time derivatives are. You aren't free to independently specify the time rate of change. Despite all the induction blather about time derivatives of fields causing values of the fields, it actually is that the values of electromagnetic fields determine the time derivatives. | |
| Apr 2, 2016 at 20:16 | comment | added | AccidentalFourierTransform | @Qmechanic essentialy a duplicate, isn't it? | |
| Apr 2, 2016 at 19:54 | comment | added | Qmechanic♦ | Related: physics.stackexchange.com/q/246808/2451 and links therein. | |
| Apr 2, 2016 at 19:47 | history | edited | Qmechanic♦ |
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| Apr 2, 2016 at 19:40 | review | First posts | |||
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| Apr 2, 2016 at 19:39 | history | asked | Ray W | CC BY-SA 3.0 |