Hertz
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- See also the car rental company, The Hertz Corporation
The hertz (symbol Hz) is the SI unit of frequency. It is named in honour 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" (1 / s); 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, or a human heart might be said to beat at 1.2 Hz.
The name hertz was adopted by the CGPM (Conférence générale des poids et mesures) in 1960, replacing the previous name for the unit, cycles per second (cps), along with its related multiples (kilocycles, megacycles, and so forth). Hertz replaced cycles in common use by 1970.
SI Multiples
| 1 kilohertz | kHz | 103 Hz | 1 000 Hz |
| 1 megahertz | MHz | 106 Hz | 1 000 000 Hz |
| 1 gigahertz | GHz | 109 Hz | 1 000 000 000 Hz |
| 1 terahertz | THz | 1012 Hz | 1 000 000 000 000 Hz |
| 1 petahertz | PHz | 1015 Hz | 1 000 000 000 000 000 Hz |
| 1 exahertz | EHz | 1018 Hz | 1 000 000 000 000 000 000 Hz |
Examples
- 10 Hz, cyclic rate of a typical automobile engine at idle (equivalent to 600 rpm)
- 50 Hz or 60 Hz (50 Hz for European AC, Tokyo AC or 60 Hz for American AC, Osaka AC), electromagnetic — standard AC mains power
- 20 Hz to ~16 kHz, acoustic — normal range of adult human hearing (most children and some animals perceive sounds outside this range)
- 100 Hz, cyclic rate of a typical automobile engine at redline (equivalent to 6000 rpm)
- 261.626 Hz, acoustic — the musical note middle C
- 440 Hz, acoustic — concert pitch (A above middle C), used for tuning musical instruments
- 740 kHz, transitions — the clock speed of the world's first commercial microprocessor, the Intel 4004 (1971)
- 1 MHz to 8 MHz, transitions — clock speeds of early home/personal computers (mid-1970s to mid-1980s)
- 30 MHz to 300 MHz, electromagnetic — VHF terrestrial TV broadcasts
- 88 MHz to 108 MHz, electromagnetic — FM radio broadcasts
- 1420 MHz, the frequency of the hyperfine transition of hydrogen, the most common element in the universe.
- 3.73 GHz, transitions — clock speed of the Pentium 4 "Prescott" microprocessor (2005)
- 428 THz to 750 THz, electromagnetic — visible light, from red to violet
- 30 PHz, electromagnetic — x-rays
Lower frequencies:
- Once per minute: about 16.67 mHz
- Hourly: about 277.8 µHz
- Daily: about 11.57 µHz
- Weekly: about 1.653 µHz
- Monthly (on average): about 380.5 nHz
- Yearly: about 31.71 nHz
- Once per decade: about 3.171 nHz, once per century: about 317.1 pHz, once per millennium: about 31.71 pHzar:هيرتز
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