Electromagnetic waves are electric and magnetic fields traveling through free space at the speed of light; in other words, an electromagnetic wave is a propagating electromagnetic field that travels with finite velocity as a disturbance through a medium. The field itself is the disturbance, rather than simply representing a physical displacement or other effect on the medium. This fact is essential to understanding how electromagnetic waves can travel through a true vacuum.
Electromagnetic waves have certain important properties; many specific characteristics of the wave, such as velocity and polarization, depend on the properties of the medium through which it propagates. The development of the disturbance also depends these properties i.e. the material exhibits ‘dispersion’ if the disturbance undergoes a change in its temporal behaviour as the wave progresses. As waves travel they carry energy and momentum away from the source. This energy may be later returned to the source or delivered to some distance location. Waves are also capable of transferring energy to or withdrawing energy from the medium through which they propagate. When energy is carried outward from the source never to return, we call the process ‘electromagnetic radiation’. Light is an electromagnetic occurrence, and many of the common characteristics of light that we identify in our daily experience may applied to all electromagnetic waves. For example, radio waves bend or refract in the ionosphere much as light waves bend while passing through a prism. Microwaves reflect from conducting surfaces in the same way that light waves reflect from a mirror; detecting these reflections forms the basis of radar. Additionally, electromagnetic waves may be ‘confined’ by reflecting boundaries to form waves standing in one or more directions. Using this concept we can employ waveguides or transmission lines to guide electromagnetic energy from spot to spot or to concentrate it in the cavity of a microwave oven.
Also read: How Light Was Classified as an Electromagnetic Wave
