a planar electromagnetic wave is propagating in the +x direction. at a certain point p and at a given instant, the electric field of the wave is given by e⃗ = (0.082 v/m) j^. what is the poynting vector at the point p at that instant? (c = 3.0 × 108 m/s, μ0 = 4π × 10-7 t •· m/a, ε0 = 8.85 × 10−12 c2/n • m2)