The hertz (symbol: Hz) is the SI unit of frequency. Its base unit is cycle/s or s^-1 (also called inverse seconds, reciprocal seconds). In English, hertz is used as both singular and plural. As any SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 10³ Hz), MHz (megahertz, 10⁶ Hz), GHz (gigahertz, 10⁹ Hz) and THz (terahertz, 10¹² Hz). Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was the German physicist and mechanician for whom the hertz, an SI unit, is named. ... The Hertz Corporation (also known as Hertz Rent A Car or simply Hertz) is the worlds second largest car rental company, with 1,900 locations in the United States and 5,100 worldwide behind Enterprise, but is the largest general use car rental company in the world. ... Hertz may refer to: Hertz Hertzian cone Hertz doctrine Hertz horn Hertz Bay Hill Classic Hertz Corporation Franck-Hertz experiment Heinrich-Hertz-Turm Hertz (crater) Surnames Eleonora Hertz Poznanski, see also Izrael PoznaÅ„ski Gustav Ludwig Hertz, German Nobel laureate physicist Heinrich (Rudolf) Hertz, German radio pioneer (Carl) Hellmuth Hertz... Tail of a 100ARW Boeing KC-135A-BN Stratotanker, Serial 58-0100, displaying the crest of RAF Mildenhall and the historic SquareD badge as used by the unit during the second world war RAF Mildenhall (IATA: MHZ, ICAO: EGUN) is a Royal Air Force station located at Mildenhall in Suffolk... MHz Networks is a Northern Virginia based public broadcasting group operated by Commonwealth Public Broadcasting Corporation. ... “SI” redirects here. ... For other uses, see Frequency (disambiguation). ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ...

One hertz simply means one cycle per second (typically that which is being counted is a complete cycle); 100 Hz means one hundred cycles 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 frequencies of aperiodic events, such as radioactive decay, are expressed in becquerels. This article is about the unit of time. ... Heart rate is a term used to describe the frequency of the cardiac cycle. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... The becquerel (symbol Bq) is the SI derived unit of radioactivity, defined as the activity of a quantity of radioactive material in which one nucleus decays per second. ...

To avoid confusion, periodically varying angles are typically not expressed in hertz, but rather in an appropriate angular unit such as radians per second. A disc rotating at 1 revolution per minute (RPM) can thus be said to be rotating at 0.105 rad/s or 0.017 Hz, where the latter reflects the number of complete revolutions per second. The conversion between Hz and rad/s is rad/s = 1 Hz × 2 . Some common angles, measured in radians. ...

History

The hertz is named after the German physicist Heinrich Rudolf Hertz, who made important scientific contributions to electromagnetism. The name was established by the IEC in 1930.^[1] It 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, primarily kilocycles per second (kc/s) and megacycles per second (Mc/s). The term cycles per second was largely replaced by hertz by the 1970s. Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was the German physicist and mechanician for whom the hertz, an SI unit, is named. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... Year 1930 (MCMXXX) was a common year starting on Wednesday (link will display 1930 calendar) of the Gregorian calendar. ... The Conférence générale des poids et mesures (General Conference on Weights and Measures or CGPM) is one of the three organizations established to maintain the SI system under the terms of the Metre Convention (1875). ...

The term “gigahertz”, most commonly used in computer processor speed and Radio Frequency (RF) applications, can be pronounced either /ˈgigaˌhɝts/, with a hard /g/ sound or /ˈʒɪgaˌhɝts/ or /ˈdʒɪgaˌhɝts/, with a soft /ʒ/ sound at the beginning of the word. The prefix “giga-” is derived directly from the Greek “γιγας” and hence the preferred pronunciation is /ˈgɪga/. Some electrical engineers use /ˈdʒɪga/, by analogy with “gigantic”.

Applications

Vibration

Sound is a traveling wave which is an oscillation of pressure. Humans perceive frequency of sound waves as pitch. Each musical note corresponds to a particular frequency which can be measured in hertz. An infant's ear is able to perceive frequencies ranging from 16 Hz to 20,000 Hz; the average human can hear sounds between 20 Hz and 15,000 Hz. ^{[citation needed]} The range of ultrasound and other physical vibrations such as molecular vibrations extends into the megahertz and well beyond. Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... This article is about pressure in the physical sciences. ... Pitch is the perceived fundamental frequency of a sound. ... For other uses, see Ultrasound (disambiguation). ... A molecular vibration occurs when atoms in a molecule are in periodic motion while the molecule as a whole has constant translational and rotational motion. ...

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. Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Oscillation is the variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. ... This article is about the unit of time. ...

Radio frequency radiation is usually measured in kilohertz, megahertz, or gigahertz; this is why radio dials are commonly labeled with kHz, MHz, and GHz. Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz. 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 gamma rays, which can be measured in exahertz. (For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum.) It has been suggested that this article or section be merged with Radio waves. ... This article does not cite any references or sources. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Image of two girls in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz, are in the region of the electromagnetic spectrum between 300 gigahertz (3x1011 Hz) and 3 terahertz (3x1012 Hz), corresponding to the wavelength range starting at submillimeter (<1 millimeter... This article is about electromagnetic radiation. ... For other uses, see Wavelength (disambiguation). ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High...

Computing

In computing, most CPUs are labeled in terms of their clock speed expressed in megahertz or gigahertz (10⁹ hertz). The number of megahertz refers to the frequency of the CPU's master clock signal ("clock speed"). This signal is simply an electrical voltage which changes from low to high and back again at regular intervals. Hertz has become the primary unit of measurement used by the general populace to determine the speed of a CPU, but many experts have criticized this approach, which they claim is an easily manipulable benchmark.^[2] For home-based personal computers, the CPU has ranged from approximately 1 megahertz in the late 1970s (Atari, Commodore, Apple computers) to nearly 4 gigahertz for modern-day Macintosh and PC machines. “CPU” redirects here. ... In synchronous digital electronics, such as most computers, a clock signal is a signal used to coordinate the actions of two or more circuits. ... “CPU” redirects here. ...

Various computer buses, such as memory buses connecting the CPU and system RAM, also transfer data using clock signals operating at different frequencies in the megahertz ranges (for modern products). In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. ... Look up RAM, Ram, ram in Wiktionary, the free dictionary. ...

Frequencies not expressed in hertz

Even higher frequencies are believed to occur naturally, in the frequencies of the quantum-mechanical wave functions of high-energy (or, equivalently, massive) particles, although these are not directly observable, and must be inferred from their interactions with other phenomena. For practical reasons, these are typically not expressed in hertz, but in terms of the equivalent energy. A wave function is a mathematical tool that quantum mechanics uses to describe any physical system. ...

Look up si, Si, SI in Wiktionary, the free dictionary. ... Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was the German physicist and mechanician for whom the hertz, an SI unit, is named. ... Majuscules or capital letters (in the Roman alphabet: A, B, C, ...) are one type of case in a writing system. ... Minuscule, or lower case, is the smaller form (case) of letters (in the Roman alphabet: a, b, c, ...). Originally alphabets were written entirely in majuscule (capital) letters which were spaced between well-defined upper and lower bounds. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ...

References

See also

• Frequency converter
• Wavelength
• Orders of magnitude (frequency)
• Bandwidth