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32-454: CBI conducted measurements at frequencies between 26 and 36 GHz in ten bands of 1 GHz bandwidth . It had a resolution of better than 1/10 of a degree. (In comparison, the pioneering COBE satellite, which produced the first detection of fluctuations in the microwave background in 1992, had a resolution of about 7 degrees.) Among the key findings of the CBI is the fact that fluctuations which have

64-548: A more detailed treatment of this and the above frequency ranges, see Electromagnetic spectrum . Gravitational waves are also described in Hertz. Current observations are conducted in the 30–7000 Hz range by laser interferometers like LIGO , and the nanohertz (1–1000 nHz) range by pulsar timing arrays . Future space-based detectors are planned to fill in the gap, with LISA operating from 0.1–10 mHz (with some sensitivity from 10 μHz to 100 mHz), and DECIGO in

96-509: A single antenna at higher frequency and similar angular resolution to obtain results comparable to the CBI. The confluence of these and other CMB experiments employing different measurement techniques in recent years is a great triumph of observational cosmology. CBI was a collaboration among a number of institutions in the US and Europe. It still closely collaborates with Chilean institutions Universidad de Chile and Universidad de Concepción through

128-472: A small size on the sky are weaker than fluctuations which have a large size on the sky, which confirmed earlier theoretical predictions. More technically, CBI was the first experiment to detect intrinsic anisotropy in the microwave background on mass scales of galaxy clusters; it provided the first detection of the Silk damping tail; it found a hint of excess power at high-l multipoles (CBI-excess) than expected from

160-584: A wavelength equal to λ = ⁠ h / p ⁠ . Combining de Broglie's postulate with the Planck–Einstein relation leads to p = h ν ~ {\displaystyle p=h{\tilde {\nu }}} or p = ℏ k . {\displaystyle p=\hbar k.} The de Broglie relation is also often encountered in vector form p = ℏ k , {\displaystyle \mathbf {p} =\hbar \mathbf {k} ,} where p

192-427: Is 1/time (T ). Expressed in base SI units, the unit is the reciprocal second (1/s). In English, "hertz" is also used as the plural form. As an SI unit, Hz can be prefixed ; commonly used multiples are kHz (kilohertz, 10  Hz ), MHz (megahertz, 10  Hz ), GHz (gigahertz, 10  Hz ) and THz (terahertz, 10  Hz ). One hertz (i.e. one per second) simply means "one periodic event occurs per second" (where

224-490: Is also used to describe the clock speeds at which computers and other electronics are driven. The units are sometimes also used as a representation of the energy of a photon , via the Planck relation E  =  hν , where E is the photon's energy, ν is its frequency, and h is the Planck constant . The hertz is defined as one per second for periodic events. The International Committee for Weights and Measures defined

256-494: Is known as the Planck constant . Several equivalent forms of the relation exist, including in terms of angular frequency ω : E = ℏ ω , {\displaystyle E=\hbar \omega ,} where ℏ = h / 2 π {\displaystyle \hbar =h/2\pi } . Written using the symbol f for frequency, the relation is E = h f . {\displaystyle E=hf.} The relation accounts for

288-401: Is the momentum vector, and k is the angular wave vector . Bohr's frequency condition states that the frequency of a photon absorbed or emitted during an electronic transition is related to the energy difference ( Δ E ) between the two energy levels involved in the transition: Δ E = h ν . {\displaystyle \Delta E=h\nu .} This is

320-484: Is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle ) per second . The hertz is an SI derived unit whose formal expression in terms of SI base units is s , meaning that one hertz is one per second or the reciprocal of one second . It is used only in the case of periodic events. It is named after Heinrich Rudolf Hertz (1857–1894),

352-452: Is usually measured in kilohertz (kHz), megahertz (MHz), or gigahertz (GHz). with the latter known as microwaves . Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens of terahertz (THz, infrared ) to a few petahertz (PHz, ultraviolet ), with the visible spectrum being 400–790 THz. Electromagnetic radiation with frequencies in the low terahertz range (intermediate between those of

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384-506: The Planck constant h . The angular forms make use of the reduced Planck constant ħ = ⁠ h / 2π ⁠ . Here c is the speed of light . The de Broglie relation, also known as de Broglie's momentum–wavelength relation, generalizes the Planck relation to matter waves . Louis de Broglie argued that if particles had a wave nature , the relation E = hν would also apply to them, and postulated that particles would have

416-475: The Planck–Einstein relation , Planck equation , and Planck formula , though the latter might also refer to Planck's law ) is a fundamental equation in quantum mechanics which states that the energy E of a photon , known as photon energy , is proportional to its frequency ν : E = h ν . {\displaystyle E=h\nu .} The constant of proportionality , h ,

448-678: The Very Small Array , operated on the island of Tenerife , and the Degree Angular Scale Interferometer , operated in Antarctica . Both of these experiments used radio interferometry to measure CMB fluctuations at lower resolution over larger areas of the sky. Another experiment operated from Antarctica, the Arcminute Cosmology Bolometer Array Receiver , used total power (bolometric) detection and

480-974: The quantized nature of light and plays a key role in understanding phenomena such as the photoelectric effect and black-body radiation (where the related Planck postulate can be used to derive Planck's law ). Light can be characterized using several spectral quantities, such as frequency ν , wavelength λ , wavenumber ν ~ {\displaystyle {\tilde {\nu }}} , and their angular equivalents ( angular frequency ω , angular wavelength y , and angular wavenumber k ). These quantities are related through ν = c λ = c ν ~ = ω 2 π = c 2 π y = c k 2 π , {\displaystyle \nu ={\frac {c}{\lambda }}=c{\tilde {\nu }}={\frac {\omega }{2\pi }}={\frac {c}{2\pi y}}={\frac {ck}{2\pi }},} so

512-559: The ΛCDM model; and it detected fluctuations in the polarization of the microwave background obtaining the first detailed E-mode polarization spectrum providing evidence that it is out of phase with the total intensity mode spectrum. The CBI was built at the California Institute of Technology , and employed sensitive radio amplifiers from the National Radio Astronomy Observatory ; two similar experiments are

544-446: The 0.1–10 Hz range. In computers, most central processing units (CPU) are labeled in terms of their clock rate expressed in megahertz ( MHz ) or gigahertz ( GHz ). This specification refers to the frequency of the CPU's master clock signal . This signal is nominally a square wave , which is an electrical voltage that switches between low and high logic levels at regular intervals. As

576-468: The 1970s. In some usage, the "per second" was omitted, so that "megacycles" (Mc) was used as an abbreviation of "megacycles per second" (that is, megahertz (MHz)). Sound is a traveling longitudinal wave , which is an oscillation of pressure . Humans perceive the frequency of a sound as its pitch . Each musical note corresponds to a particular frequency. An infant's ear is able to perceive frequencies ranging from 20 Hz to 20 000  Hz ;

608-555: The Chajnantor Observatory. In 2006, new 1.4 m antennas replaced the old 0.9 m dishes for more high-resolution studies in total intensity mode. During this stage, CBI was called CBI-2 . In June 2008, CBI-2 stopped the observations and the 13-antenna instrument was removed from its mount. The new QUIET telescope instrument was installed in August 2008 on the CBI mount, replacing CBI-2 . GHz The hertz (symbol: Hz )

640-543: The Planck relation can take the following "standard" forms: E = h ν = h c λ = h c ν ~ , {\displaystyle E=h\nu ={\frac {hc}{\lambda }}=hc{\tilde {\nu }},} as well as the following "angular" forms: E = ℏ ω = ℏ c y = ℏ c k . {\displaystyle E=\hbar \omega ={\frac {\hbar c}{y}}=\hbar ck.} The standard forms make use of

672-476: The average adult human can hear sounds between 20 Hz and 16 000  Hz . The range of ultrasound , infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtohertz into the terahertz range and beyond. 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

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704-440: The event being counted may be a complete cycle); 100 Hz means "one hundred periodic events occur 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 occurrence rate of aperiodic or stochastic events is expressed in reciprocal second or inverse second (1/s or s ) in general or, in

736-403: The first person to provide conclusive proof of the existence of electromagnetic waves . For high frequencies, the unit is commonly expressed in multiples : kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones , particularly those used in radio - and audio-related applications. It

768-449: The hertz has become the primary unit of measurement accepted by the general populace to determine the performance of a CPU, many experts have criticized this approach, which they claim is an easily manipulable benchmark . Some processors use multiple clock cycles to perform a single operation, while others can perform multiple operations in a single cycle. For personal computers, CPU clock speeds have ranged from approximately 1 MHz in

800-413: The highest normally usable radio frequencies and long-wave infrared light) is often called terahertz radiation . Even higher frequencies exist, such as that of X-rays and gamma rays , which can be measured in exahertz (EHz). 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

832-454: The late 1970s ( Atari , Commodore , Apple computers ) to up to 6 GHz in IBM Power microprocessors . Various computer buses , such as the front-side bus connecting the CPU and northbridge , also operate at various frequencies in the megahertz range. Higher frequencies than the International System of Units provides prefixes for are believed to occur naturally in the frequencies of

864-747: The quantum-mechanical vibrations of massive particles, although these are not directly observable and must be inferred through other phenomena. By convention, these are typically not expressed in hertz, but in terms of the equivalent energy, which is proportional to the frequency by the factor of the Planck constant . The CJK Compatibility block in Unicode contains characters for common SI units for frequency. These are intended for compatibility with East Asian character encodings, and not for use in new documents (which would be expected to use Latin letters, e.g. "MHz"). Planck relation The Planck relation (referred to as Planck's energy–frequency relation ,

896-544: The rules for capitalisation of a common noun ; i.e., hertz becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case. The hertz is named after the German physicist Heinrich Hertz (1857–1894), who made important scientific contributions to the study of electromagnetism . The name was established by the International Electrotechnical Commission (IEC) in 1935. It

928-409: The second as "the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium -133 atom" and then adds: "It follows that the hyperfine splitting in the ground state of the caesium 133 atom is exactly 9 192 631 770  hertz , ν hfs Cs = 9 192 631 770  Hz ." The dimension of the unit hertz

960-413: The specific case of radioactivity , in becquerels . Whereas 1 Hz (one per second) specifically refers to one cycle (or periodic event) per second, 1 Bq (also one per second) specifically refers to one radionuclide event per second on average. Even though frequency, angular velocity , angular frequency and radioactivity all have the dimension T , of these only frequency is expressed using

992-480: The unit hertz. Thus a disc rotating at 60 revolutions per minute (rpm) is said to have an angular velocity of 2 π  rad/s and a frequency of rotation of 1 Hz . The correspondence between a frequency f with the unit hertz and an angular velocity ω with the unit radians per second is The hertz is named after Heinrich Hertz . As with every SI unit named for a person, its symbol starts with an upper case letter (Hz), but when written in full, it follows

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1024-482: 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

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