P.8-27 A uniform plane wave in air with E(z) = a,10e 6 (V/m) is incident normally on an interface at z=0 with a lossy medium having a dielectric constant 2.5 and a loss tangent 0.5. Find the following: a) The instantaneous expressions for E,(z, t), H,(z, t), E,(z, t), and H,(z, t), using a cosine reference. b) The expressions for time-average Poynting vectors in air and in the lossy medium.