# Hertz

MHzkHzHzGHzmegahertzkilohertzgigahertzTHzterahertzhertz (Hz)
The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as cycles per one second.wikipedia
19,164 Related Articles

### SI derived unit

derived unitderived unitsJ/kg
The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as cycles per one second.
The SI has special names for 22 of these derived units (for example, hertz, the SI unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m 2 ), the SI derived unit of area; and the kilogram per cubic metre (kg/m 3 or kg⋅m −3 ), the SI derived unit of density.

### Heinrich Hertz

Heinrich Rudolf HertzHertzHeinrich Rudolph Hertz
It is named after Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves.
The unit of frequency, cycle per second, was named the "Hertz" in his honor.

### Cycle per second

kilocyclecycles per secondkilocycles
The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as cycles per one second. 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 cycle per second was a once-common English name for the unit of frequency now known as the hertz (Hz).

Some of the unit's most common uses are in the description of sine waves and musical tones, particularly those used in radio- and audio-related applications.
Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz).

### Frequency

frequenciesperiodperiodic
The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as cycles per one second.
The SI derived unit of frequency is the hertz (Hz), named after the German physicist Heinrich Hertz.

### International System of Units

SISI unitsSI unit
The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as cycles per one second.

### Second

ssecmegasecond
The International Committee for Weights and Measures defined 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."
Although the historical definition of the unit was based on this division of the Earth's rotation cycle, the formal definition in the International System of Units (SI) is a much steadier timekeeper: it is defined by taking the fixed numerical value of the caesium frequency ∆ν Cs, the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s −1.

### Becquerel

BqMBqPBq
The occurrence rate of aperiodic or stochastic events is expressed in reciprocal second or inverse second (1/s or s −1 ) in general or, in the specific case of radioactive decay, in becquerels.
Other names considered were hertz (Hz), a special name already in use for the reciprocal second, and Fourier (Fr).

### International Electrotechnical Commission

IECInternational Electrotechnical Commission (IEC)(IEC)
The name was established by the International Electrotechnical Commission (IEC) in 1930.
The IEC was instrumental in developing and distributing standards for units of measurement, particularly the gauss, hertz, and weber.

### Caesium

cesiumCsCs +
The International Committee for Weights and Measures defined 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."
Although it has a large nuclear spin (7⁄2+), nuclear magnetic resonance studies can use this isotope at a resonating frequency of 11.7 MHz.

### Ultrasound

ultrasonicultrasonicsultrasounds
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.
This limit varies from person to person and is approximately 20 kilohertz (20,000 hertz) in healthy young adults.

### Infrasound

infrasonicInfrasonic Soundsubsonic
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.
Infrasound, sometimes referred to as 'low-frequency sound', is sound that is lower in frequency than 20 Hz or cycles per second, the "normal" limit of human hearing.

### Angular frequency

angular rateangular speedangular frequencies
Even though angular velocity, angular frequency and the unit hertz all have the dimension 1/s, angular velocity and angular frequency are not expressed in hertz, but rather in an appropriate angular unit such as radians per second.
From the perspective of dimensional analysis, the unit hertz (Hz) is also correct, but in practice it is only used for ordinary frequency f, and almost never for ω.

### Planck constant

Planck's constantreduced Planck constantreduced Planck's constant
The units are sometimes also used as a representation of energy, via the photon energy equation (E=hν), with one hertz equivalent to h joules.
where the frequency is expressed in terms of radians per second instead of cycles per second or hertz) it is often useful to absorb a factor of

### Molecular vibration

vibrationalvibrational stateVibrational transition
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.
The typical frequencies of molecular motions, known as the vibrational frequencies, range from less than 10 13 Hz to approximately 10 14 Hz, corresponding to wavenumbers of approximately 300 to 3000 cm −1.

### Light

visible lightvisiblelight source
Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz.
This wavelength means a frequency range of roughly 430–750 terahertz (THz).

### Infrared

IRnear-infraredinfra-red
Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz.
IR wavelengths extend from the nominal red edge of the visible spectrum at 700 nanometers (frequency 430 THz), to 1 millimeter (300 GHz).

### Inverse second

reciprocal secondreciprocal secondsinverse seconds
The occurrence rate of aperiodic or stochastic events is expressed in reciprocal second or inverse second (1/s or s −1 ) in general or, in the specific case of radioactive decay, in becquerels.

terahertzTHzT-Ray
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.
Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency (THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the ITU-designated band of frequencies from 0.3 to 30 terahertz (THz).

### Photon energy

photon energiesenergyenergetic
The units are sometimes also used as a representation of energy, via the photon energy equation (E=hν), with one hertz equivalent to h joules.
An FM radio station transmitting at 100 MHz emits photons with an energy of about 4.1357 × 10 −7 eV.

### Electromagnetic spectrum

spectrumspectraspectral
(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.)
The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 10 25 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus.

### General Conference on Weights and Measures

CGPMConférence Générale des Poids et MesuresCGPM conference
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).

### Sound

audiosound wavesound waves
Sound is a traveling longitudinal wave which is an oscillation of pressure.
Humans normally hear sound frequencies between approximately 20 Hz and 20,000 Hz (20 kHz), The upper limit decreases with age.

### Megahertz myth

easily manipulable benchmarkever-increasing clock speedsMHz myth
As 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.
The megahertz myth, or in more recent cases the gigahertz myth, refers to the misconception of only using clock rate (for example measured in megahertz or gigahertz) to compare the performance of different microprocessors.

### Clock rate

clock speedclock frequencyclock
It is also used to describe the clock speeds at which computers and other electronics are driven.
It is measured in clock cycles per second or its equivalent, the SI unit hertz (Hz).