4. (5 points) We have derived the the probability current in 1-dimension j(r, t) = h V) . 2mi Evaluate it for the wave function (plane wave) V(x, t) = Aexp(- (px - Et)) , h and express it in terms of velocity v of the particle. Compare this result in quantum mechanics with the expression for the charge current density in electromagnetism j(r, t) = pv , where p is the charge density and v is the charge velocity. Do you see the analogy