The hertz (symbol: Hz) is the SI The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. It is the world's most widely used system of measurement, both in everyday commerce and in science unit of frequency Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency. Loosely speaking, 1 year is the period of the Earth's orbit around the Sun, and the Earth's rotation on its axis has defined as the number of cycles per second With the organisation of the International System of Units in 1960, the cycle per second was officially replaced by the hertz, or reciprocal second—i.e. the cycle in 'cycle per second' was dropped. Perhaps because of the convenient brevity it brings to both speech and writing, this particular mandate has been so widely adopted as to render the of a periodic phenomenon.[1] One of its most common uses is the description of sine wave The sine wave or sinusoid is a mathematical function that describes a smooth repetitive oscillation. It occurs often in pure mathematics, as well as physics, signal processing, electrical engineering and many other fields. Its most basic form as a function of time is:, particularly those used in radio and audio applications.
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Definition
Details of a heartbeat as an example of a non-sinusoidal periodic phenomenon that can be described in terms of hertz. Two complete cycles are illustrated.The hertz is equivalent to cycles per second With the organisation of the International System of Units in 1960, the cycle per second was officially replaced by the hertz, or reciprocal second—i.e. the cycle in 'cycle per second' was dropped. Perhaps because of the convenient brevity it brings to both speech and writing, this particular mandate has been so widely adopted as to render the.[2] In defining the second The second , sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time. It may be measured using a clock the CIPM The International Committee for Weights and Measures is the English name of the Comité international des poids et mesures . It consists of eighteen persons from Member States of the Metre Convention (Convention du Mètre). Its principal task is to ensure world-wide uniformity in units of measurement and it does this by direct action or by declared that "the standard to be employed is the transition between the hyperfine levels F = 4, M = 0 and F = 3, M = 0 of the ground state 2S1/2 of the caesium Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (83 °F), which makes it one of only five metals that are liquid at or near room temperature.[note 1] Caesium has physical and chemical properties similar to those of rubidium and potassium. The 133 atom, unperturbed by external fields, and that the frequency of this transition is assigned the value 9 192 631 770 hertz"[3] thereby effectively defining the hertz and the second simultaneously.
In English, hertz is used as plural. As an SI unit, Hz can be prefixed The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decimal multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol. The SI prefixes are standardized by the International; commonly used multiples are kHz (kilohertz, 103 Hz), MHz (megahertz, 106 Hz), GHz (gigahertz, 109 Hz) and THz (terahertz, 1012 Hz). One hertz simply means "one cycle per second The second , sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time. It may be measured using a clock" (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 Heart rate is the number of heartbeats per unit of time - typically expressed as beats per minute - which can vary as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and tracking of medical conditions. It is also used by individuals, at 1.2 Hz. The "frequency" (activity) of aperiodic or stochastic Stochastic means random. A stochastic process is one whose behavior is non-deterministic, in that a system's subsequent state is determined both by the process's predictable actions and by a random element. However, according to M. Kac and E. Nelson, any kind of time development (be it deterministic or essentially probabilistic) which is events, such as radioactive decay Radioactive decay is the process by which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter nuclide. For example: a carbon-14 atom emits radiation, is expressed in becquerels The becquerel is the SI derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to s−1. The becquerel is named for Henri Becquerel, who shared a Nobel Prize with Pierre and Marie Curie for their work in discovering.
Even though angular velocity In physics, the angular velocity is a vector quantity which specifies the angular speed of an object and the axis about which the object is rotating. The SI unit of angular velocity is radians per second, although it may be measured in other units such as degrees per second, revolutions per second, degrees per hour, etc. When measured in cycles or, angular frequency In physics, angular frequency ω is a scalar measure of rotation rate. Angular frequency (or angular speed) is the magnitude of the vector quantity angular velocity. The term angular frequency vector is sometimes used as a synonym for the vector quantity angular velocity and hertz all have the dimensions of 1/s, angular velocity and angular frequency are not expressed in hertz [4], but rather in an appropriate angular unit such as radians The radian is the standard unit of angular measure, used in many areas of mathematics. It describes the plane angle subtended by a circular arc as the length of the arc divided by the radius of the arc. The unit was formerly a SI supplementary unit, but this category was abolished in 1995 and the radian is now considered a SI derived unit. The SI per second. Thus a disc rotating at 60 revolutions per minute (rpm) is said to be rotating at either 2π rad/s or 1 Hz, where the former measures the angular velocity In physics, the angular velocity is a vector quantity which specifies the angular speed of an object and the axis about which the object is rotating. The SI unit of angular velocity is radians per second, although it may be measured in other units such as degrees per second, revolutions per second, degrees per hour, etc. When measured in cycles or and latter reflects the number of complete revolutions per second. The conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second are:
- ω = 2πf and .
This SI The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. It is the world's most widely used system of measurement, both in everyday commerce and in science unit is named after Heinrich Hertz Heinrich Rudolf Hertz was a German physicist who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell. He was the first to satisfactorily demonstrate the existence of electromagnetic waves by building an apparatus to produce and detect VHF or UHF radio waves. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol A symbol is something such as an object, picture, written word, sound, or particular mark that represents something else by association, resemblance, or convention. For example, a red octagon may be a symbol for "STOP". On maps, crossed sabres may indicate a battlefield. Numerals are symbols for numbers . All language consists of symbols is uppercase Capital letters or majuscules are the larger of two type faces in a script. In the Roman alphabet they are A, B, C, D, etc. They are also called capitals (caps) or upper case (uppercase). The latter name comes from the antique age of setting type for printing presses, when printers kept the type for these letters in the upper drawers of a desk or (Hz). When an SI unit is spelled out in English, it should always begin with a lowercase Lower case , minuscule, or small letters are the smaller form of letters, as opposed to upper case or capital letters, as used in European alphabets (Greek, Latin, Cyrillic, and Armenian). For example, the letter "a" is lower case while the letter "A" is upper case letter (hertz), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit to indicate a temperature interval (a difference between two temperatures" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2.
History
The hertz is named after the German A region named Germania, inhabited by several Germanic peoples, has been known and documented before AD 100. Beginning in the 10th century, German territories formed a central part of the Holy Roman Empire, which lasted until 1806. During the 16th century, northern Germany became the centre of the Protestant Reformation. As a modern nation-state, physicist Heinrich Hertz Heinrich Rudolf Hertz was a German physicist who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell. He was the first to satisfactorily demonstrate the existence of electromagnetic waves by building an apparatus to produce and detect VHF or UHF radio waves, who made important scientific contributions to the study of electromagnetism Electromagnetism is one of the four fundamental interactions of nature, along with strong interaction, weak interaction and gravitation. It is the force that causes the interaction between electrically charged particles; the areas in which this happens are called electromagnetic fields. The name was established by the International Electrotechnical Commission The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology". IEC standards cover a vast range of technologies from power (IEC) in 1930.[5] It was adopted by the General Conference on Weights and Measures The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures . It is one of the three organizations established to maintain the International System of Units (SI) under the terms of the Convention du Mètre (Metre Convention) of 1875. It meets in Sèvres (in the southwestern suburbs of Paris) (CGPM) (Conférence générale des poids et mesures) in 1960, replacing the previous name for the unit, cycles per second With the organisation of the International System of Units in 1960, the cycle per second was officially replaced by the hertz, or reciprocal second—i.e. the cycle in 'cycle per second' was dropped. Perhaps because of the convenient brevity it brings to both speech and writing, this particular mandate has been so widely adopted as to render the (cps), along with its related multiples, primarily kilocycles per second (kc/s) and megacycles per second (Mc/s), and occasionally kilomegacycles per second (kMc/s). The term cycles per second was largely replaced by hertz by the 1970s.
The term "gigahertz", most commonly used in computer processor clock rates and radio frequency Radio frequency is a rate of oscillation in the range of about 30 kHz to 300 GHz, which corresponds to the frequency of electrical signals normally used to produce and detect radio waves. RF usually refers to electrical rather than mechanical oscillations, although mechanical RF systems do exist (see mechanical filter and RF MEMS) (RF) applications, can be pronounced either /ˈɡɪɡəhɜrts/, with a hard /ɡ/ sound, or /ˈdʒɪɡəhɜrts/, with a soft /dʒ/.[6] The prefix "giga-" is derived directly from the Greek Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of "γιγας."
Applications
Vibration
Sound Sound is a travelling wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations is a traveling wave which is an oscillation of pressure Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. Humans perceive frequency of sound waves as pitch Pitch represents the perceived fundamental frequency of a sound. It is one of the four major auditory attributes of sounds along with loudness, timbre and sound source location. When the actual fundamental frequency can be precisely determined through physical measurement, it may differ from the perceived pitch because of overtones, also known as. Each musical note Notes are the "atoms" of much Western music: discretizations of musical phenomena that facilitate performance, comprehension, and analysis corresponds to a particular frequency which can be measured in hertz. An infant's ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz; the average human can hear sounds between 20 Hz and 16,000 Hz.[7] The range of ultrasound Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Although this limit varies from person to person, it is approximately 20 kilohertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound. The production of ultrasound is used in many different fields,, infrasound Infrasound is sound that is lower in frequency than 20 Hz or cycles per second, the normal limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infrasound, but at higher levels it is and other physical vibrations such as molecular vibrations A molecular vibration is excited when the molecule absorbs a quantum of energy, E, corresponding to the vibration's frequency, ν, according to the relation E=hν, where h is Planck's constant. A fundamental vibration is excited when one such quantum of energy is absorbed by the molecule in its ground state. When two quanta are absorbed the first extends into the megahertz range and well beyond.
Electromagnetic radiation
Electromagnetic radiation Electromagnetic radiation is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It comprises electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to is often described by its frequency—the number of oscillations Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes is used to be synonymous with "oscillation.& of the perpendicular electric and magnetic fields per second—expressed in hertz.
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 Light is electromagnetic radiation of a wavelength that is visible to the human eye . In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared Infrared light is electromagnetic radiation with a wavelength between 0.7 and 300 micrometres, which equates to a frequency range between approximately 1 and 430 THz) to thousands (ultraviolet Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet) 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 In physics, terahertz radiation refers to electromagnetic waves sent at frequencies in the terahertz range. It is also referred to as submillimeter radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz. The term is normally used for the region of the electromagnetic spectrum between 300 gigahertz and 3 terahertz (3x1012 Hz),. Even higher frequencies exist, such as that of gamma rays Gamma rays are electromagnetic radiation of high frequency (very short wavelength). They are produced by sub-atomic particle interactions such as electron-positron annihilation, neutral pion decay, radioactive decay, fusion, fission or inverse Compton scattering in astrophysical processes. Gamma rays typically have frequencies above 1019 Hz, and, 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 In physics, the wavelength of a sinusoidal wave is the spatial period of the wave – the distance over which the wave's shape repeats. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a characteristic of both traveling waves and or photon In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force. The effects of this force are easily observable at both the microscopic and macroscopic level, because the photon energies In physics, energy is a quantity that is often understood as the ability to perform work. This quantity can be assigned to any particle, object, or system of objects as a consequence of its physical state: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.)
Computing
In computing, most central processing units (CPU) are labeled in terms of their clock rate expressed in megahertz or gigahertz (109 hertz). This number refers to the frequency of the CPU's master clock signal ("Clock rate"). This signal is simply an electrical voltage which changes from low to high and back again at regular intervals. This signal is also referred to as a square wave. Hertz has become the primary unit of measurement accepted by the general populace to determine the performance of a CPU, but many experts have criticized this approach, which they claim is an easily manipulable benchmark.[8] For home-based personal computers, the CPU has ranged from approximately 1 megahertz in the late 1970s (Atari, Commodore, Apple computers) to up to 6 GHz in the present (IBM POWER processors).
Various computer buses, such as the front-side bus connecting the CPU and northbridge, also operate at different frequencies in the megahertz range (for modern products).
CRT television and monitor refresh rates are measured in hertz.
SI multiples
| Submultiples | Multiples | |||||
|---|---|---|---|---|---|---|
| Value | Symbol | Name | Value | Symbol | Name | |
| 10−1 Hz | dHz | decihertz | 101 Hz | daHz | decahertz | |
| 10−2 Hz | cHz | centihertz | 102 Hz | hHz | hectohertz | |
| 10−3 Hz | mHz | millihertz | 103 Hz | kHz | kilohertz | |
| 10−6 Hz | µHz | microhertz | 106 Hz | MHz | megahertz | |
| 10−9 Hz | nHz | nanohertz | 109 Hz | GHz | gigahertz | |
| 10−12 Hz | pHz | picohertz | 1012 Hz | THz | terahertz | |
| 10−15 Hz | fHz | femtohertz | 1015 Hz | PHz | petahertz | |
| 10−18 Hz | aHz | attohertz | 1018 Hz | EHz | exahertz | |
| 10−21 Hz | zHz | zeptohertz | 1021 Hz | ZHz | zettahertz | |
| 10−24 Hz | yHz | yoctohertz | 1024 Hz | YHz | yottahertz | |
| Common prefixed units are in bold face. | ||||||
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 quantum energy, which is proportional to the frequency by the factor of Planck's constant.
See also
References
- ^ "hertz". (1992). American Heritage Dictionary of the English Language, 3rded. Boston: Houghton Mifflin.
- ^ "SI brochure: Table 3. Coherent derived units in the SI with special names and symbols". http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html. Retrieved 20102025.
- ^ "[Resolutions of the CIPM, 1964 - Atomic and molecular frequency standards"]. http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf. Retrieved 2010-20-26.
- ^ "SI brochure, Section 2.2.2, paragraph 6". http://www.bipm.org/en/si/derived_units/2-2-2.html.
- ^ IEC History
- ^ "Gigahertz" in Dictionary.com Unabridged. Dictionary.
- ^ Dominant spectral region
- ^ Good Riddance, Gigahertz
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Q. My monitor is only 60hz!!! Its gonna cause me eye strains and it already probably did. I am getting a new graphics card cause my intergrated one sucks will the new graphics card let me make my monitor to higher hertz?
Asked by rupok93 - Tue Jan 27 14:19:08 2009 - - 2 Answers - 0 Comments
A. The max refresh rate of your monitor is a fixed value. The graphics card will only improve Frames per second when you're playing games etc. Since your eyes see everything at around 24 FPS, anything above that will appear smooth.
Answered by Curious M. Ind - Tue Jan 27 14:30:35 2009
