Answer Happy

pushed (3.4) Plasma Oscillation*& Consider a slab of metal of thickness d in the â di- rection (and arbitrary area perpendicular to this). If the electron density in the metal is displaced in the +î direction, charge builds up on the bound- ary of the slab, and an electric field results in the slab (like in a plate capacitor). The electrons in the metal respond to the electric field and are back to their original position. This restoring force (like a Hooke's law spring) results in oscillations of electron density, known as a plasma oscillation. (a)* Assume the metal is very clean. Use the finite frequency Drude conductivity in zero magnetic field (see Exercise 3.1.e with B set to zero) and calculate the plasma frequency of the metal. b (b)** Consider the case where the scattering time T is not infinite. What happens to the plasma fre- quency? How do you interpret this? (c)** Set the scattering time to oo again, but let the magnetic field be nonzero. What happens to the plasma frequency now?