A thin layer of metal transmits electromagnetic radiation according to the approximation
where t is the transmitted fraction of the energy, 
and 
are the real and the imaginary part of the conductivity,
d is the thickness of the metal, and 
[MKSA units] or
[CGS units].
(a) Assume that a superconductor is described by 
; the Cooper pair condensate results in
a delta function
at zero frequency. Calculate the transmission coefficient t
for low, but nonzero frequencies, and show that the frequency dependence
of the transmission can be used to evaluate 
.
(b) Based on the Drude model (with 
), estimate the
(super)conduction electron density n, if t=0.02 for
-cm-wavelength IR radiation. The thickness of the film
is d=1000 Å.
Laszlo Mihaly
Thu Oct 31 13:23:11 EST 1996
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