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<p><b>New page</b></p><div>[[File:Max_Planck_Wirkungsquantums_20050815.jpg|Max Planck Wirkungsquantums 20050815|thumb]] {{Short description|Physical constant in quantum mechanics}}<br />
{{Infobox constant<br />
| name = Planck constant<br />
| image = <br />
| caption = <br />
| symbol = h<br />
| dimension = [[Action (physics)|Action]]<br />
| value = 6.62607015×10⁻³⁴<br />
| units = [[Joule|J]]·[[second|s]]<br />
| uncertainty = <br />
| references = <br />
}}<br />
<br />
The '''Planck constant''' (denoted as '''''h''''') is a fundamental [[physical constant]] that is central to [[quantum mechanics]]. It describes the size of the discrete units, or [[quanta]], of [[energy]] that are involved in [[quantum phenomena]]. The Planck constant is named after the German physicist [[Max Planck]], who first introduced it in 1900.<br />
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== Definition and Value ==<br />
The Planck constant is defined as exactly 6.62607015×10⁻³⁴ [[Joule|J]]·[[second|s]]. This definition was adopted by the [[International System of Units|SI]] in 2019, based on the fixed numerical value of the constant.<br />
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== Significance in Quantum Mechanics ==<br />
The Planck constant is crucial in the field of quantum mechanics. It appears in the [[Heisenberg uncertainty principle]], which states that the position and momentum of a particle cannot both be precisely determined at the same time. The constant also features in the [[Schrödinger equation]], which describes how the quantum state of a physical system changes over time.<br />
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== Planck's Relation ==<br />
Planck's relation links the energy (E) of a photon to its frequency (ν) through the equation:<br />
:E = hν<br />
This relation is fundamental in the study of [[quantum optics]] and [[photonics]].<br />
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== Reduced Planck Constant ==<br />
The reduced Planck constant, also known as '''h-bar''' (ℏ), is defined as:<br />
:ℏ = h / 2π<br />
It is commonly used in [[quantum mechanics]] and appears in the [[Dirac equation]] and [[quantum field theory]].<br />
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== Applications ==<br />
The Planck constant is used in various applications, including:<br />
* [[Quantum computing]]<br />
* [[Spectroscopy]]<br />
* [[Photovoltaics]]<br />
* [[Quantum cryptography]]<br />
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== See Also ==<br />
* [[Max Planck]]<br />
* [[Quantum mechanics]]<br />
* [[Heisenberg uncertainty principle]]<br />
* [[Schrödinger equation]]<br />
* [[Photon]]<br />
* [[Quantum optics]]<br />
* [[Dirac equation]]<br />
* [[Quantum field theory]]<br />
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== Related Pages ==<br />
* [[Physical constant]]<br />
* [[International System of Units]]<br />
* [[Quantum computing]]<br />
* [[Spectroscopy]]<br />
* [[Photovoltaics]]<br />
* [[Quantum cryptography]]<br />
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[[Category:Physical constants]]<br />
[[Category:Quantum mechanics]]<br />
[[Category:Fundamental physics concepts]]<br />
[[Category:Max Planck]]<br />
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