The electric-field of a uniform plane wave traveling downward in water is given by E=5e-0.2 cos(wt-0.2z) (V/m) where 2 is the downward direction and z = 0 is the water surface. If σ = 4 S/m. i. 11. What is the characteristic impedance of water, magnitude and phase Find the magnetic field H 111. iv. Obtain an expression for the average power density Determine the depth at which the power density has been reduced by 10-4