Plasma frequency and electrical conductivity an organic conductor has been found by optical studies to have w_p = 1.80 x 10¹⁵ s^-1 for the plasma frequency, and τ = 2.83 x 10^-15 s for the electron relaxation time at room temperature.

(a) Calculate the electrical conductivity from these data. The carrier mass is not known and is not needed here. Take ε(∞) = 1. Convert the result to units (Ω cm)^–1. 

(b) From the crystal and chemical structure, the conduction electron concentration is 4.7 x 10²¹ cm^–3 Calculate the electron effective mass m.