1
$\begingroup$

The idea of the material Maxwell equation is almost clear. But I'm curious about the idea that except for material equation the pure Maxwell equation should work, but in harder sense: more currents and charges.

There are plenty of vacuum in solid body, so, I think, that there should be some precursors of electro-magnetic waves that propagates through the body: $v = c/n$ the speed of wave in body, but part of wave propagates in vacuum with the speed of $c$. And for any frequency some part of amplitude would be observed much earlier.

Is there some theory behind this and does this phenomena is observed?

Improve this question
$\endgroup$
1

1 Answer 1

Reset to default
1
$\begingroup$

$n$ depends on the wave frequency. For high frequencies $n\rightarrow 1$. So for a general electromagnetic field each harmonic propagates with its own speed.

EDIT: In order to speak of a front propagation, you have to have a whole spectrum of harmonics that exist always and everywhere. Each harmonic does not have a front in space, it is their superposition who has. In other words, a front "spreads out" due to frequency dispersion of waves in material.

Improve this answer
$\endgroup$
2
  • $\begingroup$ Yes, but I mean that for any wave frequency some of it would be observed much earlier. $\endgroup$
    – m0nhawk
    Commented Nov 23, 2012 at 20:23
  • $\begingroup$ @m0nhawk: In order to speak of a front propagation, you have to have a whole spectrum of harmonics that exist always and everywhere. Each harmonic does not have a front in space, it is their superposition who has. In other words, a front "spreads out" due to frequency dispersion of waves in material. $\endgroup$
    – Vladimir Kalitvianski
    Commented Nov 23, 2012 at 20:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.