HOW ARE THE ELECTROMAGNETIC WAVES GENERATED?

An accelerating or oscillating electric charge such as an electron generates an oscillating electric field, and an oscillating electric field generates an oscillating magnetic field. These fields are perpendicular

FIGURE 1: An electronic oscillator connected to an antenna produces electromagnetic waves that propagate in space.

to each other and produce electromagnetic waves that travel with some velocity. The frequency of the electromagnetic wave is the same as the frequency of mechanical oscillation of the charge, and the intensity of the electromagnetic wave is the square of the amplitude of the mechanical oscillation of the charge. An electronic oscillator connected to an antenna produces electromagnetic waves.
By constructing an oscillator that oscillates at any frequency, different electromagnetic waves with different frequencies can be generated. The schematic in Figure 1 shows generation of electromagnetic waves by an oscillator.
The electromagnetic spectrum shown in Figure 2 shows all types of electromagnetic waves.

FIGURE 2: The electromagnetic spectrum covers a wide range of wavelengths and photon energies. Light used to see an object must have a wavelength about the same size or smaller than the object. This image is taken from NASA website, with permission under the public domain license.