How do EM waves propagate?

Are the EM fields really moving.

Classically, electromagnetic waves are propagating disturbances in the electric and magnetic fields.

Remember, the electric field of a point charge extends to infinity. It does not simply stop somewhere.

When the point charge is briefly accelerated, a disturbance in the field (and the associated magnetic field) propagates with speed c outward away from the point charge.

The disturbance will continue to propagate even after the point charge has stopped accelerating; the disturbance has "a life of its own".

There's a nice applet for visualizing this here:

But, do keep in mind that we must ultimately understand electromagnetic radiation in terms of photons and that requires quantum field theory.


So EM waves are just Changes in electric fields that seem to propogate along space.

As I wrote above: electromagnetic waves are propagating disturbances in the electric and magnetic fields. Now, how and why does that happen?

But i have seen people on this site saying it happens because of continous induction of Electric and Magnetic Field. How can i relate both of these?

Think carefully about what I wrote above: the disturbance has "a life of its own" and think about how that might be.


The answer to your questions requires that you understand how EM waves are generated. Imagine an electron which is not moving and stationary. According to Coulomb's law, a field is produced by this electron. The field will be static and not changing as long the electron isn't moving.

Imagine now you start to vibrate the electron in a sinusoidal way. What is going to happen to the field? The field will be changed in a way that conforms to the motion you're doing to the electron. Basically this change in the field is an EM wave, which is travelling at the speed of light.

So yes, the EM field's change moves, like the book has told you.

A cute simulation is available at this website (link changed because the first one doesn't work):

https://www.youtube.com/watch?v=DOBNo654pwQ

Hope this helps.