# Effect of magnetic field on radio waves!

Hello all

I have been trying for sometime now to find the effects that magnetic field has on radio waves (such as cell phone signals and wireless broadband signals). If anyone of you could guide me towards right direction, would be very much appreciated!

Thanks

Ashutosh

vanhees71
Gold Member
Within the classical theory of electromagnetism electromagnetic fields are not self-interacting, i.e., nothing happens to your radio wave, whether or not other electromagnetic fields are present.

In QED due to quantum effects the em. field becomes self-interacting, but this effect can be neglected for practical purposes with radio waves.

Staff Emeritus
Easy. No effect.

really even in QED it self interacts?

vanhees71
Gold Member
Sure, that's the four-photon vertex. In leading order it's a box diagram with four external photon legs and electron-positron lines running around the box. It's a fourth-order effect inperturbation theory, i.e., of order $$\alpha^2$$ in the cross section. This is also known as the "Delbrück-scattering diagrams".

Staff Emeritus
Let's get real here. Yes, there is an infinitesmally small QED effect. One that is absolutely undetectable with radio waves and magnets.

This is one thing I am growing to dislike about this forum. Someone asks a simple question with a simple answer, and a bunch of people confuse the OP with technically correct and utterly irrelevant complications. Needlessly complicating a problem does not make one look smart.

vanhees71
Gold Member
I emphasized already in my first reply that the QED corrections are negligible for all practical purposes. Nevertheless I think it's good to answer questions correctly according to our present knowledge of physics.