The nonlinear generation of second harmonic electromagnetic waves in a thin inhomogeneous (dense and rarefied) plasma layer (of length d) by obliquely and normal incidence of light wave is analyzed. We consider the effect of external time- dependent magnetic field on the generation and amplification of waves. Two cases are considered, when the magnetic field oscillates at frequency: (i) equal, and (ii) double of that of the incident wave. For normal incidence, waves are not radiated in case (i), while in case (ii) the second harmonics are radiated equally from the plasma boundaries at x = o and x = d. For rarefied plasma, the second harmonics are radiated with equal amplitudes in both cases. (author). 3 refs.