# Hertz

The **hertz** (symbol: **Hz**) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second.[1] It is named after Heinrich Rudolf Hertz (1857-1894), the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (10^{3} Hz, kHz), megahertz (10^{6} Hz, MHz), gigahertz (10^{9} Hz, GHz), terahertz (10^{12} Hz, THz), petahertz (10^{15} Hz, PHz), exahertz (10^{18} Hz, EHz), and zettahertz (10^{21} Hz, ZHz).

Hertz | |
---|---|

Unit system | SI derived unit |

Unit of | Frequency |

Symbol | Hz |

Named after | Heinrich Hertz |

In SI base units | s^{−1} |

Some of the unit's most common uses are in the description of sine waves and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. The units are sometimes also used as a representation of energy, via the photon energy equation (*E*=*h*ν), with one hertz equivalent to *h* joules.