8.3 A plane wave traveling in a medium with er, = 9 is normally incident upon a second medium with ₁₂ = 4. Both media are made of nonmagnetic, nonconducting materials. If the magnetic field of the incident plane wave is given by H₁ = 22 cos(2π x 10⁹t - ky) (A/m). (a) Obtain time-domain expressions for the electric and magnetic fields in each of the two media. (b) Determine the average power densities of the incident, reflected, and transmitted waves.