How is an electromagnetic wave generated?
According to Maxwell’s hypothesis, the once begun process of changing the electromagnetic field in a certain area of space further captures more and more new areas. This is how, in Maxwell’s terminology, disturbances of the electromagnetic field arise. For a qualitative illustration of the propagation of an alternating electromagnetic field, let us turn to experiments with a conductor in which a direct current flows. Around such a conductor there will be a constant magnetic field that does not change in time, i.e., the magnetic induction at each point of the field does not change over time. There will be no disturbances of the electromagnetic field in the space surrounding the conductor. Let’s replace direct current with alternating current. When the current strength in the conductor changes in the surrounding space, the magnetic induction will change. An alternating magnetic field will create a vortex electric field. In turn, the changing electric field will create a magnetic field, etc. This is how an electromagnetic field arises, which begins to propagate in a certain area of space at a certain speed.