Elektronvolt: Verskil tussen weergawes

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==Using electronvolts to measure mass==
== Using electronvolts to measure mass ==
[[Albert Einstein]] reasoned that energy is equivalent to [[mass]], as famously expressed in the [[mass-energy equivalence]] formula ''E'' = ''mc''² (1.0000 [[kilogram|kg]] = 89.876 [[petajoule|PJ]]). It is thus common in particle physics, where mass and energy are often interchanged, to use eV/''c''² or even simply eV as a unit of mass.
[[Albert Einstein]] reasoned that energy is equivalent to [[mass]], as famously expressed in the [[mass-energy equivalence]] formula ''E'' = ''mc''² (1.0000 [[kilogram|kg]] = 89.876 [[petajoule|PJ]]). It is thus common in particle physics, where mass and energy are often interchanged, to use eV/''c''² or even simply eV as a unit of mass.


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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).
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==
== Electronvolts and energy ==
For comparison:
For comparison:


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*The typical atmospheric molecule has a kinetic energy of about [[1 E-21 J|1/40 eV]]. This corresponds to [[room temperature]].
*The typical atmospheric molecule has a kinetic energy of about [[1 E-21 J|1/40 eV]]. This corresponds to [[room temperature]].


==Electronvolts and photon properties==
== Electronvolts and photon properties ==


The energy ''E'', frequency ν, and wavelength λ of a photon are related by
The energy ''E'', frequency ν, and wavelength λ of a photon are related by
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An electronvolt is also the energy of an infrared photon with a wavelength of approximately 1240nm. 10eV would correspond to UV of 124nm, etc.
An electronvolt is also the energy of an infrared photon with a wavelength of approximately 1240nm. 10eV would correspond to UV of 124nm, etc.


==Using electronvolts to measure time and distance==
== Using electronvolts to measure time and distance ==
In [[particle physics]], distances and times are sometimes expressed in inverse electronvolts via the conversion factors<ref>K. Hagiwara et al, ''Review of Particle Physics'', Phys. Rev. '''D66''', 010001 (2002)</ref>
In [[particle physics]], distances and times are sometimes expressed in inverse electronvolts via the conversion factors<ref>K. Hagiwara et al, ''Review of Particle Physics'', Phys. Rev. '''D66''', 010001 (2002)</ref>


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In these units, the [[exponential decay|mean lifetime]] <math>\tau</math> of an unstable particle can be reexpressed in terms of its ''decay width'' <math>\Gamma</math> (in eV) via <math>\Gamma = \hbar/\tau</math>. For example, the [[List of mesons|B<sup>0</sup> meson]] has a mean lifetime of 1.542(16) [[picosecond]]s, or a decay width of 4.269(44) x 10<sup>-4</sup> eV, and its mean decay length is <math>c\tau</math> = 462 <math>\mu</math>m.
In these units, the [[exponential decay|mean lifetime]] <math>\tau</math> of an unstable particle can be reexpressed in terms of its ''decay width'' <math>\Gamma</math> (in eV) via <math>\Gamma = \hbar/\tau</math>. For example, the [[List of mesons|B<sup>0</sup> meson]] has a mean lifetime of 1.542(16) [[picosecond]]s, or a decay width of 4.269(44) x 10<sup>-4</sup> eV, and its mean decay length is <math>c\tau</math> = 462 <math>\mu</math>m.


==Electronvolts and temperature==
== 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 [[kelvin]]s (symbol: uppercase K) is defined by using ''k<sub>B</sub>'', the [[Boltzmann constant]]:
In certain fields, such as [[plasma physics]], it is convenient to use the electronvolt as a unit of temperature. The conversion to [[kelvin]]s (symbol: uppercase K) is defined by using ''k<sub>B</sub>'', the [[Boltzmann constant]]:


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For example, a typical [[magnetic confinement fusion]] plasma is 15 keV, or 174 megakelvins.
For example, a typical [[magnetic confinement fusion]] plasma is 15 keV, or 174 megakelvins.


==See also==
== See also ==
*[[Orders of magnitude (energy)]]
*[[Orders of magnitude (energy)]]
*[[Thermodynamics]]
*[[Thermodynamics]]
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== Verwysings ==
== Verwysings ==
{{verwysings}}
{{Verwysings}}


[[Kategorie:Eenhede]]
[[Kategorie:Eenhede]]

Wysiging soos op 02:43, 9 September 2018

Die elektronvolt (simbool eV) is 'n eenheid van energie. Dit is die hoeveelheid kinetiese energie wat 'n enkele onverbonde elektron verkry as dit deur 'n elektrostatiese potensiaalverskil van een volt in 'n vakuum versnel word. In ander woorde gestel is dit gelyk aan een volt (1 volt = 1 joule per coulomb) vermenigvuldig met die lading van 'n enkele elektron.

'n Elektronvolt is 'n baie klein hoeveelheid energie:

1 eV = 1.602 176 53 e−19 J. [1] (of ongeveer 0.160 aJ)

Die elektronvolt as eenheid word deur die SI aanvaar (maar nie aangemoedig nie). Dit word algemeen gebruik in Vastetoestand-, Kern- en partikelfisika, dikwels saam met die voorvoegsels m, k, M, G of T.

Ionisasie-energieë en ander atoomeienskappe word dikwels aangehaal in terme van elektronvolt, veral in ouer tekste.

Verwysings

  1. Peter J. Mohr en Barry N. Taylor, CODATA recommended values of the fundamental physical constants: 2002, Reviews of Modern Physics, Januarie 2005, volume=77 bladsye=1–107, PDF afgelaai op 2006-07-01, 'n In diepte bespreking oor hoe die CODATA konstantes gekies en bepaal is.