Electromagnetic radiation, illustrated in , is a form of energy emitted and absorbed by charged particles. As it travels through space It behaves like waves, and has components of both electric and magnetic field. These waves oscillate perpendicularly to and in phase with one another. Electromagnetic waves are a specific case of electromagnetic fields, and are produced by moving charges. These charges produce both near-field and far-field effects, but it is the far-field that is electromagnetic radiation (accordingly, that will be the focus of this atom).
The genesis of all electromagnetic waves begins with a charged particle. This charged particle has an electric field, which exerts a force on other nearby charged particles. When it moves, the charged particle not only maintains its electric field, but also produces a magnetic field, which in turn exerts force on nearby moving charges.
It should be added that once in motion, the electric and magnetic fields created by a charged particle are self-perpetuating—time-based changes in one field (electric or magnetic) affect the other. This means that an electric field that oscillates as a function of time time will produce a magnetic field, and a magnetic field that changes as a function of time will produce an electric field. As shows, both electric and magnetic fields in an electromagnetic wave will fluctuate in time, one causing the other to change. If a particle becomes charged while in motion, the resulting scenario is very much like the case of the "chicken and the egg" causality dilemma.
Electromagnetic waves are ubiquitous in modern technology—AM and FM radio, cordless and cellular phones, garage door openers, wireless networks, radar, microwave ovens, etc. These and many more such devices use electromagnetic waves to transmit data and signals.
All the above sources of electromagnetic waves use the simple principle of moving charge, which can be easily modeled. Placing a coin in contact with both terminals of a 9-volt battery produces electromagnetic waves that can be detected by bringing the antenna of a radio (tuned to a static-producing station) within a few inches of the point of contact.