The radiation of energy as transverse waves that is produced by moving charges. A charge can radiate electromagnetic radiation only if it is undergoing accelerated motion. There is one exception: a charge moving at a constant velocity through a dielectric can emit Cherenkov radiation. Electromagnetic radiation is also known as an electromagnetic wave, and consists of oscillating electric and magnetic fields at right angles to one another and to the propagation direction. Electromagnetic radiation comes in discrete packets known as photons.
In a vacuum, electromagnetic radiation prorogates at the speed of light c, and at a speed
in matter, where n is the index of refraction of the given material. Electromagnetic radiation has a characteristic wavelength (and frequency ), with the two related by
The following table summarizes the names given to electromagnetic radiation based on its wavelength.
Electromagnetic Wave, Gamma Ray, Infrared, Microwave, Multipole Radiation, Near Infrared, Radar, Radio Wave, Submillimeter, Ultraviolet, Visible Light, X-Ray
