The Josephson effects occur if two superconductors are weakly coupled, e.g. by separating them by an insulating layer of a few nanometer in thickness. Irradiation of this Josephson junction with microwaves (being an electromagnetic wave) creates between the superconductors discrete voltage levels depending only on the ratio of two fundamental constants and the frequency f of the microwaves. These steps of constant voltage are generated at voltages Vn :