Problem: Frequency-Dependent Response of a Superconductor

            Assume that the real part of the conductivity of a superconductor is described by . In a nearly free-electron model, how is A related to the electron density, mass and charge? Calculate the penetration depth, , and the reflectivity coefficient, , for . (Hint: A way to approximate the Dirac-delta function is to use a Drude conductivity with with a relaxation time .)