ductor, while rubber (o silver (σ = 6.1 x 107 S/m, u, = 1, &, = 1) is a good con- = 10-15 S/m, μ, = 1, ɛ, = 3.1) is a good insulator. 10.11 Seawater plays a vital role in the study of submarine communications. Assuming that for seawater, σ = 4 S/m, &, = (b) the wavelength, (c) the skin depth, (d) the intrinsic impedance. 80, μ, = 1, and f = 100 kHz, calculate (a) the phase velocity, 10.12 In a certain medium with u=u