Planck's constant

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Planck's constant (h)

Etymology: Max Planck, German physicist, 1858-1947
a fundamental physical constant that relates the energy of radiation to its frequency. It is expressed as 6.63 × 10-27 erg-seconds or 6.63 × 10-34 joule-seconds. See also photon.


The basic unit of radiant energy defined by the equation
E = hν
where h is Planck's constant (6.62 ✕ 10−34 joule ✕ second), ν the frequency of the light and E the energy difference carried away by the emission of a single photon of light. The term photon usually refers to visible light whereas the term quantum refers to other electromagnetic radiations. See quantum theory; wave theory; troland.
References in periodicals archive ?
Their subsequent adjustment in their new measurements both increased their value of Planck's constant and reduced the uncertainty in their measurement.
The watt balance and atom-counting techniques now give nearly identical values of Planck's constant, with an uncertainty of less than 20 parts in a billion, says metrologist Ian Robinson of the National Physical Laboratory in Teddington, England.
But then, we are not working with Planck's constant.
In addition, Werner Heisenberg (a collaborator of Bohr) proposed his now-famous uncertainty principle, which stated that Planck's constant is used to define the ultimate limit of the accuracy of measurements of subatomic particles.
This is the basic definition of Planck's constant h in terms of the Lame spacetime constants and the Burgers spacetime dislocation constant [b.
In each such allowed orbit the electron possessed an angular momentum equal to a multiple of Planck's constant divided by 2 pi.
The electrons that surround the nucleus of an atom can only occupy certain discrete states--those states being defined by Planck's constant, h.
In the preceding equation, h is Planck's constant and c, the speed of light.
Since Planck's constant is exceedingly small, energy has a very fine grain indeed, and it is not noticeable in most circumstances, so that the laws of thermodynamics could be deduced as though energy were a continuous fluid without grain.
It should be observed that if we examine this question from a quantum mechanical perspective we are inevitably struck by the fact that the role of Planck's constant in gravitational wave phenomena has always been taken for granted without questions regarding the possible limits of its applicability being asked, which is somewhat perplexing since no purely gravitational measurement of Planck's constant exists.
Because we measure resistance and voltage based on fundamental constants - electron charge and Planck's constant - being able to measure current would also allow us to confirm the universality of these constants on which many precise measurements rely.