# Thread: How does electromagnetic wave travel?

1. I know that electromagnetic wave is a combination of 2 mutually perpendicular electric and magnetic wave, and the varying electric wave produces magnetic wave, which again produces electric wave and so it propagates (correct me if I am wrong). Now my question is How can such a varying electric field / magnetic field traverse through space. The varying field is something that varies at a particular point / location in space. Isn't it? So if such a varying field is gonna produce an another type of varying field, perpendicular in this case, it will make that in the same position. Right? If it is, how is em wave traversing through the space? ie how is the shift in position of variation of fields happen ? I hope question is clear.

2. Originally Posted by jijoPaulK
I know that electromagnetic wave is a combination of 2 mutually perpendicular electric and magnetic wave, and the varying electric wave produces magnetic wave, which again produces electric wave and so it propagates (correct me if I am wrong). Now my question is How can such a varying electric field / magnetic field traverse through space. The varying field is something that varies at a particular point / location in space. Isn't it? So if such a varying field is gonna produce an another type of varying field, perpendicular in this case, it will make that in the same position. Right? If it is, how is em wave traversing through the space? ie how is the shift in position of variation of fields happen ? I hope question is clear.
B and E "leapfrog" each other, see pictures

3. Originally Posted by AndrewC
B and E "leapfrog" each other, see pictures
I understand the variation of fields with respect to time. But how does that variation propagate through space?

4. Originally Posted by jijoPaulK
I understand the variation of fields with respect to time. But how does that variation propagate through space?
B amd E vary BOTH in time AND in space (see the pics I linked in)

5. Originally Posted by AndrewC
B amd E vary BOTH in time AND in space (see the pics I linked in)
I saw that animation. It is shown in spatial x,y,z directions and wave is traversing in y direction. Right? But my question is HOW!? When a charged particle is accelerated, it creates a varying field near to the particle, and such varying electric field will produce a varying magnetic field. But this variation happens only with respect to time. Right? How is that variation moving forward???

6. Originally Posted by jijoPaulK
I saw that animation. It is shown in spatial x,y,z directions and wave is traversing in y direction. Right? But my question is HOW!? When a charged particle is accelerated, it creates a varying field near to the particle, and such varying electric field will produce a varying magnetic field. But this variation happens only with respect to time. Right? How is that variation moving forward???
No, B=B(X,t) and E=E(Z,t)
What you see is the Pointing vector,

7. Originally Posted by AndrewC
No, B=B(X,t) and E=E(Z,t)
What you see is the Pointing vector,
I think you're not getting what I'm asking. Anyway thanks for your time.

8. Originally Posted by jijoPaulK
I think you're not getting what I'm asking. Anyway thanks for your time.
The Poynting vector is the wavefront. I am getting what you ask, you aren't getting my answer.

9. As an analogy, I suppose you could consider that the E field pushes B forward as it changes and B pushes E forward as it changes.

Or, even more simply, it wouldn't be a wave if it didn't move through space as well as time!

10. Originally Posted by Strange
As an analogy, I suppose you could consider that the E field pushes B forward as it changes and B pushes E forward as it changes.

Or, even more simply, it wouldn't be a wave if it didn't move through space as well as time!
So, Is there a phase difference between these 2 waves?

11. Originally Posted by jijoPaulK
So, Is there a phase difference between these 2 waves?
They are in phase, see here and here