Speed of light in a superconductor

[Domenicaccio]

Could you please spot where is the fault in this reasoning? I suspect that some of the relations may not be applicable and needs to be substituted with something else (or I'm just making a gross mistake as usual...):

Speed of light in a material:

c=\sqrt{\frac{1}{\epsilon\mu}}

where permettivity is

\mu=\mu_r\mu_0

and suscettivity is

\chi_m=\mu_r - 1

which describes the magnetization of the material due to an external magnetic field

M=\chi_m H

-------------------------

A superconductor behaves like a perfectly diamagnetic material, suppressing the internal field B because

\chi_m = - 1

M=-H

therefore

\mu_r = 0

\mu = 0

c=infinite

which clearly makes no sense...

 

[yoyoq]

there are also negative index of refraction materials
which also mess that up.

i think the subtlety is the phase vs group velocity
of the light waves.http://en.wikipedia.org/wiki/Phase_velocity

"...The phase velocity of electromagnetic radiation may under certain circumstances (e.g. in the case of anomalous dispersion) exceed the speed of light in a vacuum, but this does not indicate any superluminal information or energy transfer..."

 

[Ben Niehoff]

Also, in a perfect conductor, \epsilon = \infty. I don't know if this applies to superconductors (but they do offer practically zero resistance, yes?).

 

[kanato]

IIRC, the penetration depth of light into a conductor is proportionate to the resistivity, so in a perfect conductor light won't penetrate at all (the charge carries at the surface absorb all the light that isn't reflected).

 

[Vanadium 50]

What you are discovering is that you don't have electromagnetic radiation inside an ideal superconductor.