Main Page | See live article | Alphabetical index zh-cn:赫兹 The hertz (symbol Hz) is the SI unit of frequency. It is named in honor of the German physicist Heinrich Rudolf Hertz who made some important contributions to science in the field of electromagnetism. One hertz simply means "one per second"; 100 Hz means "one hundred per second", and so on. The unit may be applied to any periodic event – for example, a clock might be said to tick at 1 Hz. In older writings, the equivalent unit cycle per second (cps) is seen. SI Multiples 1 kilohertz (symbol kHz) = 103 Hz = 1,000 Hz 1 megahertz (symbol MHz) = 106 Hz = 1,000,000 Hz 1 gigahertz (symbol GHz) = 109 Hz = 1,000,000,000 Hz 1 terahertz (symbol THz) = 1012 Hz = 1,000,000,000,000 Hz 1 petahertz (symbol PHz) = 1015 Hz = 1,000,000,000,000,000 Hz 1 exahertz (symbol EHz) = 1018 Hz = 1,000,000,000,000,000,000 Hz Examples 50 or 60 Hz, electromagnetic – standard AC electric power supplies 261.625 Hz, acoustic – the musical note middle C 440 Hz, acoustic – concert pitch (A above middle C), used for tuning musical instruments 104 kHz, transitions – the clock speed of the first commercially produced microprocessor, the Intel 4004 (1971) 1 to 8 MHz, transitions – clock speeds of early home/personal computers (late 1970s, early-to-mid 1980s) 88 to 108 MHz, electromagnetic – FM radio broadcasts 2.2 GHz, transitions – clock speed of the Pentium 4 microprocessor (2002) 460 THz, electromagnetic – red light 30 PHz, electromagnetic – x-rays This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.