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It’s a fairly simple question. Basically, my physics teacher said that EM waves work like in the image I posted here. An electric field creates a magnetic field in the same place, then this magnetic field creates an electric field in the place forward. However, intuitively, I think this is wrong, but I’m not 100% sure.

I know that electric fields can create magnetic fields and vice versa, but I always thought they would happen at the same place, same time. Intuitively, I think EM waves are like this animation here: https://youtu.be/oZZ4wKYtVl8

Basically, continuous disturbances that just happen to occur both in magnetic and electric fields at the same time.

Which interpretation is correct?

Qmechanic
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  • It’s not really a physics course, I’m studying for exams to enter med school, so I wouldn’t be surprised if my teacher taught me wrong, as it wouldn’t make much of a difference in respect to exams. Just curious –  Oct 30 '17 at 17:43
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    @RobertoValente - no picture in physics is really correct - only the math is 'correct'. But the picture is often enough to understand the phenomena enough to work with it – Martin Beckett Oct 30 '17 at 17:49
  • But it’s not just the picture.. the interpretation is slightly different too. Basically, do magnetic waves induce the apparition of the electric field in the place forward? Or the EM wave works more like a regular wave, a continuos disturbance on both fields, that happen simultaneously? What’s the way you understand the phenomenon? –  Oct 30 '17 at 17:55
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    See https://physics.stackexchange.com/questions/363992/how-to-read-maxwells-equations/363997#363997 – ProfRob Oct 30 '17 at 22:12
  • From a purely mathematical standpoint, I think what your teacher meant is that the derivative at a point will determine the value of the field at the point after a time dt, which is to say by Faraday’s law for example (and an amperian analogue) that Curl(E)dt=-dB, which is how dB evolves after dt, by a factor of -Curl(E). Same goes for amperian which says Curl(B)dt=dE, this governs how the E field (dE) will change after a small time dt. But yes I agree that a differential equation of any physical significance only applies to a specific time – Russell Yang Nov 01 '17 at 03:21

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You cannot find an electrical wave without a magnetic wave. There is a reason why they are called the electromagnetic waves because they are just one wave and their effect is observed in different dimensions (one operates in X then the other operates in Y).

I think your teacher was trying to explain you the concept of magnetic flux. In order to see current, you need to have a change in magnetic field. You can read up on Maxwell equations and Faraday law.

Your diagram is correct and the video which is just the dynamic version of the image is also correct. The correct word to use would be change rather than disturbance and it happens at the same time because if one field exists then the other field also exists and they both cause each other to exists and you can imagine that there is no time gap if that is what's bothering you.

LostCause
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  • Makes sense. It’s that, the way my teacher said it, it didn’t even sound like a wave in a sense. Just a series of steps of one field creating the other, and the other inducing another in a place forward. I picture it as something more “continuous” like a disturbance on surface of water (obviously on EM there are the 2 dimensions). Not a series of inductions in chain, does it make sense? –  Oct 30 '17 at 18:23