The hertz (symbol: Hz) is the SI unit of frequency. Its base unit is s^-1 (also called inverse seconds, or 1/s). In English, hertz is used as both singular and plural. Cover of brochure The International System of Units. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...

One hertz simply means "one cycle per second"; 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 frequency of aperiodic events, such as radioactive decay, are expressed in becquerels. Look up second in Wiktionary, the free dictionary. ... Heart rate is a term used to describe the frequency of the cardiac cycle. ... 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 radian is a unit of plane angle. ...

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 (kc) and megacycles (Mc). The term cycles per second was largely replaced by hertz by the 1970's. Heinrich Hertz Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894), was the German physicist and mechanician for whom the hertz, the SI unit, is named. ... Electromagnetism is the physics of the electromagnetic field; a field encompassing all of space 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 initials IEC can stand for: Independent Electoral Commission Industrial Emergency Council Inertial electrostatic confinement (in fusion energy) Institut des Experts-comptables et des Conseils fiscaux Institut dEstudis Catalans, Catalan Studies Institute Interactive Evolutionary Computation International Education Centre International Electrical Congress International Electrotechnical Commission See also IEC connector for... 1930 (MCMXXX) was a common year starting on Wednesday (link is to a full 1930 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). ...

SI multiples

Applications

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 radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... Look up second in Wiktionary, the free dictionary. ...

Radio frequency radiation is usually measured in kilohertz, megahertz, or gigahertz; this is why radio dials are commonly labelled with kHz, MHz, and GHz. Rough plot of Earths atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including radio waves. ...

Sound is a travelling 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 scientifically measured in hertz. Although the human ear is able to perceive frequencies ranging from 16 Hz to 20,000 Hz, the average human can hear sounds between 20 Hz and 16,000 Hz. Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... In music, pitch is the psychological correlate of the fundamental frequency of a note. ...

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. 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. ...

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. ...

This SI unit is named after Heinrich Rudolf Hertz. As for all SI units whose names are derived from the proper name of a person, the first letter of its symbol is uppercase (Hz). But when an SI unit is spelled out, it should always be written in lowercase (hertz), unless it begins a sentence or is the name "degree Celsius". — Based on The International System of Units, section 5.2.

Image File history File links SI_Brochure_Cover. ... Cover of brochure The International System of Units. ... Heinrich Hertz Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894), was the German physicist and mechanician for whom the hertz, the 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. ... The Celsius scale is a temperature scale named after the Swedish astronomer Anders Celsius (1701 â€“ 1744), who first proposed a similar system two years before his death. ...

See also

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