Electronvolt
Electron volt - Wikipedia, the free encyclopedia
So an electron volt (electronvolt according to the NIST) is 1 volt ... convenient to use the electronvolt as a unit of temperature. ... of the electronvolt ...
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electron volt: Definition from Answers.com
electron volt n. ( Abbr. eV ) A unit of energy equal to the energy acquired by an electron falling through a ... BIPM's definition of the electronvolt ...
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Measurement unit conversion: electronvolt
Electronvolt is a measure of energy. ... electronvolt to zeptojoule. electronvolt to tonne of coal equivalent ... electronvolt to kilopond meter. electronvolt ...
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Units: E
One electronvolt is the work required to move an electron through a potential ... An energy of 1 electronvolt is therefore equivalent to a mass of about 1.782 662 ...
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Electronvolt - Simple English Wikipedia, the free encyclopedia
The electronvolt is often used in atomic, nuclear and particle physics. ... Retrieved from "http://simple.wikipedia
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electronvolt. Common Units. Energy and Work Conversion Chart
electronvolt conversion chart page. Energy and Work conversion online. Instant online units and measurements conversion: for metric conversion and other systems. ...
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electronvolt definition | Dictionary.com
Definition of electronvolt at Dictionary.com with free ... electronvolt. electronystagmograph... electrooculogram ... for: electronvolt ...
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Energy - convert from electronvolt unit to electronvolt - Convert ...
Energy - convert from electronvolt unit to electronvolt. Online weights and measures conversion. Online calculators for quick and easy metric conversion, conversion ...
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electronvolt
electron volt. A unit of energy, equal to the amount of kinetic energy acquired ... For a more precise value, consult the most recent CODATA table. ...
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electronvolt - Definition of electronvolt at Your Dictionary
Electronvolt synonyms. Electronvolt pronunciation and usage examples. Electronvolt quotes. ... entries near electronvolt " electronics " electronically " ...
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The electronvolt (symbol eV) is a unit of energy. In theoretical physics, where distinctions between mass and energy are not concrete, it is often used also as a unit of mass (AAAS Science journal, 2006). It is the amount of kinetic energy gained by a single unbound electron when it passes through an Electrostatics potential difference of one volt, in vacuo. In other words, it is equal to one volt (1 volt = 1 joule per coulomb) times the (unsigned) elementary charge. The one-word spelling is the modern recommendation NIST: Units outside the SI, although the use of the earlier electron volt still exists.
One electronvolt is a very small amount of energy: 1 eV = 1 E-19 J joule. An in-depth discussion of how the CODATA constants were selected and determined. (or approximately 0.160 atto-J)
The unit electronvolt is accepted (but not encouraged) for use with SI. It is widely used in Solid-state physics, Atomic physics, Nuclear physics, and particle physics, often with SI prefix m, k, M, G or T. In a recorded lecture from 1961 Richard Feynman apologized to his students for this failure by atomic physicists to use the appropriate SI unit (which would be the atto-joule): "A single atom is such a small thing that to talk about its energy in joules would be inconvenient. But instead of taking a definite unit in the same system, like 10−20 J, have unfortunately chosen, arbitrarily, a funny unit called an electronvolt (eV) ... I am sorry that we do that, but that's the way it is for the physicists." Transcript of part of a 1961 lecture by Richard Feynman
In chemistry, it is often useful to have the molar equivalent, that is the kinetic energy that would be gained by a mole (unit) of electrons passing through a potential difference of one volt. This quantity is equal to 1 E4 J Joule per mole. Ionization energy and other atomic properties are often quoted in electronvolts, especially in older texts.
Using electronvolts to measure mass Albert Einstein reasoned that energy is equivalent to mass, as famously expressed in the mass-energy equivalence formula E = mc² (1.0000 kilogram = 89.876 petajoule). It is thus common in particle physics, where mass and energy are often interchanged, to use eV/c² or even simply eV as a unit of mass.
For example, an electron and a positron, each with a mass of 0.511 MeV/c², can annihilate to yield 1.022 MeV of energy. The proton has a mass of 0.938 GeV/c², making GeV a very convenient unit of mass for particle physics. 1 eV/c² = 1.783 kg 1 keV/c² = 1.783 kg 1 MeV/c² = 1.783 kg 1 GeV/c² = 1.783 kg 1 TeV/c² = 1.783 kg 1 PeV/c² = 1.783 kg 1 EeV/c² = 1.783 kg See: Orders of magnitude (mass)
In some older documents, and in the name Bevatron, the symbol "BeV" is used, which stands for "billion-electron-volt"; it is equivalent to the GeV (gigaelectronvolt).
Electronvolts and energy For comparison:
- 3.2 joule or 200 MeV - total energy released in nuclear fission of one U-235 atom (on average; depends on the precise break up)
- 3.5 joule or 210 MeV - total energy released in fission of one Pu-239 atom (also on average)
- Molecular bond energy are on the order of an electronvolt per molecule.
- The typical atmospheric molecule has a kinetic energy of about 1 E-21 J. This corresponds to room temperature.
Electronvolts and photon properties The energy E, frequency f, and wavelength λ of a photon are related by
E=hf=\frac{hc}{\lambda}= \frac{1240~\rm{nm~eV-->{\lambda}
where h is Planck's constant and c is the speed of light. For example, the spectrum of visible light consists of wavelengths ranging from 400 nm to 700 nm. Photons of visible light therefore have energies ranging from
E_{min} = \frac{1240~\rm{nm~eV-->{700~\rm{nm--> = 1.77~\rm{eV}
to
E_{max} = \frac{1240~\rm{nm~eV-->{400~\rm{nm--> = 3.10~\rm{eV}.
An electronvolt is also the energy of an infrared photon with a wavelength of approximately 1240 nm. Similarly, 10eV would correspond to ultraviolet of wavelength 124 nm, and so on.
Using electronvolts to measure time and distance In particle physics, distances and times are sometimes expressed in inverse electronvolts via the conversion factorsK. Hagiwara et al, Review of Particle Physics, Phys. Rev. D66, 010001 (2002)
- \hbar = 6.582 118 89(26) x 10-16 eV s
- \hbar c = 197.326 960 2(77) eV nm
In these units, the mean lifetime \tau of an unstable particle can be reexpressed in terms of its decay width \Gamma (in eV) via \Gamma = \hbar/\tau. For example, the List of mesons has a mean lifetime of 1.542(16) picoseconds, or a decay width of 4.269(44) x 10-4 eV, and its mean decay length is c\tau = 462 \mum.
Electronvolts and temperature In certain fields, such as plasma physics, it is convenient to use the electronvolt as a unit of temperature. The conversion to kelvins (symbol: uppercase K) is defined by using kB, the Boltzmann constant:
{1 \mbox{ eV} \over k_B} = {1.60217653(14) \times 10^{-19} \mbox{J} \over 1.3806505(24) \times 10^{-23} \mbox{J/K--> = 11604.505(20) \mbox{ kelvins}
For example, a typical magnetic confinement fusion plasma is 15 keV, or 174 megakelvins.
References
See also
- Orders of magnitude (energy)
- Thermodynamics
External links
- BIPM's definition of the electronvolt
- http://physics.nist.gov/cuu/Constants physical constants reference; CODATA data
Electronvolt - Wikipedia, the free encyclopedia
The electronvolt (symbol eV) is a unit of energy. It is the amount of energy equivalent to that gained by a single unbound electron when it is accelerated through an electrostatic ...
www.ast.leeds.ac.uk
What is an electron volt? An electron volt, or eV for short, is a measure of energy. It is quite a small amount of energy similar to the amount of energy possessed by a ...
Electronvolt - Hutchinson encyclopedia article about Electronvolt
Mass and energy are equivalent, according to Einstein, and scientists have noticed that the energy scale associated with dark energy, about one-thousandth of an electronvolt, is ...
electronvolt - definition of electronvolt by the Free Online ...
electronvolt. Noun. Physics a unit of energy equal to the work done on an electron accelerated through a potential difference of 1 volt
Electronvolt - definition of Electronvolt in the Medical dictionary ...
eV electron volt. eV or ev. abbr. electron volt. eV. electron volt.
Definition: electron-volt from Online Medical Dictionary
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Electron volt - Wikipedia, the free encyclopedia
In physics, the electron volt (eV) is a unit of energy. By definition, it is equal to the amount of energy gained by a single unbound electron when it accelerates through an ...
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Electronvolt definition of Electronvolt in the Free Online ...
Electronvolt. A unit of energy used for convenience in atomic systems. Specifically, it is the change in energy of an electron, or of any particle having a charge numerically equal ...
electron volt - Hutchinson encyclopedia article about electron volt
electron volt. Unit for measuring the energy of a charged particle (ion or electron) in terms of the energy of motion an electron would gain from a potential difference of one volt ...