(1) Accelerated charges radiate electromagnetic waves. The frequency of the electromagnetic wave naturally equals the frequency of oscillation of the charge. The energy associated with the propagating wave comes at the expense of the energy of the source – the accelerated charge.
(2) Hertz’s experiment (1887) produced low frequency region (the radio wave region).
(3) Jagdish Chandra Bose, working at Calcutta, produced electromagnetic waves of much shorter wavelength (25 mm to 5 mm).
(4) Guglielmo Marconi in Italy succeeded in transmitting electromagnetic waves over distances of many kilometres.
