Problem 6 (25 points) (Chap 9) (Learning objective: Plane waves) 9.5-1 A uniform plane wave propagating in free space has an electric field intensity equal to êЕo cos (wt + [1 rad/m] + [2 rad/m] y + [3 rad/m] 2). The direction of "e" is not specified. (a) What is the unit vector that points in the direction of propagation? Be as specific as possible. (b) What is the wavelength in this material? (c) What is the frequency of the wave?