In this paper, we present the explicit derivation of the electromagnetic (EM) field solution of Maxwell equations starting from the Dirac equation, used in describing the so-called spinor wave function of quantum particles. In particular, we show that if the four-component vector (spinor) solution of the Dirac equation for zero mass is identified with the four-potential of the EM field, then, under the Lorentz gauge, fields derived from that potential satisfy Maxwell equations. Vice versa, the four-potential could be used to express a spinor solution, provided that the latter satisfies the Lorenz gauge. Some examples in the frequency domain clarify this connection. A crucial choice is needed: the EM potential has to be assumed as a linear c...