Lights flash at frequency f = 0.5 Hz (Hz = hertz), 1.0 Hz and 2.0 Hz, where Failed to parse (Missing texvc executable; please see math/README to configure.): x

Hz means Failed to parse (Missing texvc executable; please see math/README to configure.): x
flashes per second. T is the period and T = Failed to parse (Missing texvc executable; please see math/README to configure.): y
s (s = second) means that Failed to parse (Missing texvc executable; please see math/README to configure.): y

is the number of seconds per flash. T and f are each other's reciprocal: f = 1/T and T = 1/f.

The hertz (symbol Hz) is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon.^[1] One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications. The word "hertz" is named for Heinrich Rudolf Hertz, who was the first to conclusively prove the existence of electromagnetic waves.

Definition[link]

The hertz is equivalent to cycles per second.^[2] In defining the second, the CIPM 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 2S_1/2 of the cesium 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 a plural.^[4] As an 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). 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 "frequency" (activity) of aperiodic or stochastic events, such as radioactive decay, is expressed in becquerels.

Even though angular velocity, angular frequency and hertz all have the dimensions of 1/s, angular velocity and angular frequency are not expressed in hertz,^[5] but rather in an appropriate angular unit such as radians 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 and the 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:

Failed to parse (Missing texvc executable; please see math/README to configure.): \omega = 2\pi f \,

and Failed to parse (Missing texvc executable; please see math/README to configure.): f = \frac{\omega}{2\pi} \, 

. This SI unit is named after Heinrich Hertz. As with every International System of Units (SI) unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (Hz). When an SI unit is spelled out in English, it should always begin with a lower 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" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2.

History[link]

The hertz is named after the German physicist Heinrich Hertz who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission (IEC) in 1930.^[6] It was adopted by the General Conference on Weights and Measures (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), 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 (RF) applications, can be pronounced either /ˈɡɪɡəhɜrts/, with a hard /ɡ/ sound, or /ˈdʒɪɡəhɜrts/, with a soft /dʒ/^[7] (see giga-#Pronunciation). The prefix "giga-" is derived directly from the Greek "γιγας" ("giant").

Applications[link]

Sine waves of different frequency.

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.

Vibration[link]

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 20 Hz to 20,000 Hz; the average adult human can hear sounds between 20 Hz and 16,000 Hz.^[8] The range of ultrasound, high-intensity infrasound and other physical vibrations such as molecular vibrations extends into the megahertz range and well beyond.

Electromagnetic radiation[link]

Electromagnetic radiation is often described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz.

Radio frequency radiation is usually measured in kilohertz (kHz), megahertz (MHz), or gigahertz (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.)

Computing[link]

In computing, most central processing units (CPU) are labeled in terms of their clock rate expressed in megahertz or gigahertz (10⁶ or 10⁹ hertz, respectively). 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 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.^[9] 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) and up to 8 GHz overclocked (AMD FX processors).^[10]

Various computer buses, such as the front-side bus connecting the CPU and northbridge, also operate at different frequencies in the megahertz range

[edit] SI multiples

Frequencies not expressed in hertz[link]

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[link]

References[link]

External links[link]

• BIPM Cesium ion f_Cs definition
• National Research Council of Canada: Generation of the Hz
• National Research Council of Canada: Cesium fountain clock
• National Physical Laboratory: Trapped ion optical frequency standards
• National Research Council of Canada: Optical frequency standard based on a single trapped ion
• National Research Council of Canada: Optical frequency comb
• One Hertz in Radians per Second (Google). Note, as of 06 May 2009 there is an error of 2Failed to parse (Missing texvc executable; please see math/README to configure.): \pi

.

v t e SI units Base units Ampere · Candela · Kelvin · Kilogram · Metre · Mole · Second Derived units Becquerel · Coulomb · Degree Celsius · Farad · Gray · Henry · Hertz · Joule · Katal · Lumen · Lux · Newton · Ohm · Pascal · Radian · Siemens · Sievert · Steradian · Tesla · Volt · Watt · Weber Accepted for use with SI Dalton (Atomic mass unit) · Astronomical unit · Day · Decibel · Degree Celsius · Degree of arc · Electronvolt · Hectare · Hour · Litre · Minute · Minute of arc · Neper · Second of arc · Tonne Atomic units · Natural units See also SI prefixes · Systems of measurement · Conversion of units · New SI definitions · History of the metric system Book:International System of Units  · Category:SI base units

This article has multiple issues. Please help improve it or discuss these issues on the talk page. This biography of a living person needs additional citations for verification. Tagged since July 2008. Its references may not meet Wikipedia's guidelines for reliable sources. Tagged since August 2011. It may contain improper references to self-published sources. Tagged since August 2011.

Ill Bill
Ill Bill, also known as Billy Crystal
Background information
Birth name	William Braunstein
Born	(1972-07-14) July 14, 1972 (age 39)
Origin	Brooklyn, New York, U.S.
Genres	Hip hop
Occupations	Rapper Producer Label CEO
Years active	1991–present
Labels	Uncle Howie Psycho+Logical
Associated acts	Non Phixion La Coka Nostra Circle of Tyrants Secret Society Injustice Necro DJ Muggs Jedi Mind Tricks
Website	www.illbill.com www.unclehowie.com

William Braunstein, better known as Ill Bill, is a Jewish American Rapper and record producer from Brooklyn, New York. Having gained notoriety in the underground hip hop group Non Phixion, Ill Bill is known for his hardcore lyrics and as the producer, founder and CEO of Uncle Howie Records. His brother Ron is also a rapper and producer, known as Necro.^[1]

Biography[link]

Ill Bill was the main voice behind the now disbanded Non Phixion, and is currently involved with La Coka Nostra, along with Slaine, Danny Boy and DJ Lethal of House of Pain & Limp Bizkit fame. In 2004 he released his debut solo album What's Wrong with Bill? and has since released various solo mixtapes and collaborations in anticipation for his second solo record and the upcoming La Coka Nostra album.

NYC 1998

On September 16, 2008, he released his second album on Uncle Howie Records, entitled The Hour of Reprisal. The album includes appearances from Necro, Tech N9ne, B-Real of Cypress Hill, Everlast, Bad Brains, Max Cavalera of Soulfly, Vinnie Paz of Jedi Mind Tricks, Howard Jones of Killswitch Engage, Immortal Technique and Raekwon of Wu-Tang Clan. It also features production by DJ Muggs, T-Ray, DJ Lethal, Necro, DJ Premier and Ill Bill himself.

He released an album with Vinnie Paz as the Heavy Metal Kings. Ill Bill was supposed to release a collaboration album with rapper Crooked I and production team Blue Sky Black Death, but the project was cancelled.

During Spring 2008, Ill Bill joined Tech N9ne and Paul Wall on a nationwide tour. "The Hour of Reprisal" was released on September 16, 2008 by Uncle Howie Records and Fat Beats.

In an October 31, 2010 interview on Conspiracy Worldwide Radio, Ill Bill discussed his relationship with his brother Necro and his range of albums expected in 2011 including La Coka Nostra, The Pill album with Sean Price and his Heavy Metal Kings album with Vinnie Paz set to release April 5, 2011.^[2]

[edit] What's Wrong with Bill?

What's Wrong with Bill? is Ill Bill's debut studio album, released on March 2, 2004 by Psycho+Logical-Records. The album spawned one single, "The Anatomy of a School Shooting", and a music video for "Chasing the Dragon". This album never charted.^[3]

Discography[link]

• 2001: The Early Years: Rare Demos '91-'94
• 2002: The Future Is Now (with Non Phixion)
• 2003: ILL BILL Is The Future
• 2003: Street Villains (with Necro)
• 2003: Howie Made Me Do It
• 2004: The Green CD/DVD (with Non Phixion)
• 2004: What's Wrong with Bill?
• 2005: Street Villains 2 (with Necro)
• 2005: Circle Of Tyrants (with Necro, Goretex & Mr. Hyde)
• 2006: ILL BILL Is The Future Vol. 2
• 2007: Black Metal
• 2008: The Hour of Reprisal
• 2009: A Brand You Can Trust (with La Coka Nostra)
• 2010: Kill Devil Hills (with DJ Muggs)
• 2011: Heavy Metal Kings (with Vinnie Paz)
• 2011: Howie Made Me Do It 2
• 2012: Masters Of The Dark Arts (with La Coka Nostra)
• 2012: The Grimy Awards ^[4]
• 2012: Heavy Metal Kings vs. DJ Muggs ^[4]
• TBA: The Pill (with Sean Price) ^[5]
• TBA: Heavy Metal Kings 2

Collaborations[link]

• Sha-key feat. Ill Bill "Doompasaga"(produced by Ill Bill) off the LP "A Head Nadda's Journey To Adidi Skizm" (1994 Imago Recording Company)
• Necro feat. Ill Bill & Goretex "I Need Drugs" LP (2001 Psycho+Logical)
• O.D. feat. Ill Bill & Goretex of Non Phixion "2004" 12" (1999 Audio Research)
• Company Flow feat. Ill Bill of Non Phixion "Simian Drugs" 12" (2000 Def Jux)
• Necro feat. Ill Bill "The Most Sadistic" 12" (2000 Psycho+Logical)
• Necro feat. Ill Bill & Goretex "Gory Days" LP (2001 Psycho+Logical)
• Troy Dunnit feat. Ill Bill "Let's Go" 12" (2001 Audio Research)
• Non Phixion (Ill Bill, Goretex, Sabac Red & DJ Eclipse) "The Future Is Now" LP (2002 Uncle Howie)
• El-P feat. Ill Bill "Fantastic Damage" LP (2002 Def Jux)
• The Beatnuts feat. Ill Bill, Problemz - "Yae Yo" 12" (2002 Landspeed)
• Jedi Mind Tricks feat. Ill Bill, Sabac Red - "The Wolf" 12" (2003 Babygrande)
• Dj JS-1 feat. Ill Bill, Licence to ill- "Ground Original" LP (2003 Yosumi / M3)
• Non Phixion (Ill Bill, Goretex, Sabac Red & DJ Eclipse) "The Green CD/DVD" (2004 Uncle Howie)
• Circle Of Tyrants (Necro, Ill Bill, Goretex & Mr. Hyde) "The Circle Of Tyrants" LP (2005 Psycho+Logical)
• Necro and Ill Bill "Street Villains Vol. 2" (2005 Psycho+Logical)
• Ill Bill feat. Raekwon - "Enemy" (2006) (White Label)
• Ill Bill feat. Raekwon - "Thousands To M's" (2006) (White Label)
• MC Lars feat. Ill Bill - "The Dialogue" (extraído del álbum de MC Lars "The Graduate" 2006)
• Jedi Mind Tricks feat. Ill Bill - "Heavy Metal Kings" (2006 Babygrande Records)
• La Coka Nostra (Danny Boy, Ill Bill, Everlast, Slaine, Big Left, Kaves & DJ Lethal) LP (Próximamente)
• Ill Bill Feat Slaine & Reef The Lost Cause "Bangmatic Remix" (Mass Movementz The Album, 2009)
• Clementino feat. Ill Bill - "Hannibal rapper" (2011 Relief Records)

References[link]

External links[link]

• www.illbill.com