Editing Hertz (section)

==={{anchor|Electricity}} Electromagnetic radiation===
[[Electromagnetic radiation]] is often described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz.

Radio frequency radiation is usually measured in kilohertz (kHz), megahertz (MHz), or gigahertz (GHz). with the latter known as [[microwave]]s. [[Light]] is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens of terahertz (THz, [[infrared]]) to a few petahertz (PHz, [[ultraviolet]]), with the [[visible spectrum]] being 400–790&nbsp;THz. Electromagnetic radiation with frequencies in the low terahertz range (intermediate between those of the highest normally usable radio frequencies and long-wave infrared light) is often called [[terahertz radiation]]. Even higher frequencies exist, such as that of [[X-ray]]s and [[gamma ray]]s, which can be measured in exahertz (EHz).

For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their [[wavelength]]s or [[Photon energy|photon energies]]: for a more detailed treatment of this and the above frequency ranges, see ''[[Electromagnetic spectrum]]''.