Planck's constant


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Planck's constant

(plängks), fundamental constant of the quantum theoryquantum theory,
modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.
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. It is represented by the letter h and has a value of 6.62607 × 10−34 joule-second. The combination h/2π, denoted by h (called "h-bar"), occurs frequently.
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Planck's constant

A fundamental physical constant which represents the elementary quantum of action, action being defined as energy multiplied by time. Introduced by Max Planck in 1900, it has the value h = 6.6261 × 10-27 erg-second or 6.6261 × 10-34 joule-second. The symbol ℏ, sometimes called the Dirac h, is often used for convenience in physics to denote the quantity h/2π, where π = 3.1416….

As used by Planck in deriving his radiation law, h multiplied by the frequency of radiation represented a bundle of energy, that is, a quantum of energy. Radiant energy at any wavelength can occur only as multiples of this energy; thus energy is quantized. See Compton effect, Fundamental constants, Heat radiation, Quantum mechanics

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Planck’s Constant

 

(the quantum of action), a fundamental physical constant that determines a broad range of physical phenomena characterized by discreteness of action. These phenomena are studied in quantum mechanics. Planck’s constant was introduced by M. Planck in 1900 in establishing the law of energy distribution in a blackbody radiation spectrum. The symbol for the constant is h.

The most accurate value for Planck’s constant has been obtained on the basis of the Josephson effect: h = (6.626176 ± 0.000036) × 10–34 joule-Hz–1 = (6.626176 ± 0.000036) × 10–27 erg-Hz–1. The constant = h/2π = (1.0545887 ± 0. 0000057) × 10–27 erg-Hz–1, which is more often used, is also called Planck’s constant.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

Planck's constant

[′pläŋks ‚kän·stənt]
(quantum mechanics)
A fundamental physical constant, the elementary quantum of action; the ratio of the energy of a photon to its frequency, it is equal to 6.62606876 ± 0.00000052 × 10-34 joule-second. Symbolized h. Also known as quantum of action.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
All of these new values of the Planck's constant do not overlap, "but overall they're in amazingly good agreement," Schlamminger said, "especially considering that researchers are measuring it with two completely different methods." These values will be submitted to a group known as CODATA ahead of a July 1 deadline.
In this way Planck's constant was born Planck named his constant h and calculated it to be 6 55 X [10.sup.-27] erg-seconds.
In each such allowed orbit the electron possessed an angular momentum equal to a multiple of Planck's constant divided by 2 pi.
Not only were electrons prohibited from assuming orbits in between the discrete ones allowed by Planck's constant, they could not even momentarily be in these states.
He worked out the relationship between energy and wavelength (or energy and frequency, since frequency is 1 divided by the wavelength), making use of a very small value called Planck's constant, which represents the "graininess" of energy.
In this paper, we explore the relation between the spacetime Burgers dislocation constant [b.sub.0] and Planck's constant, and derive the value of the spacetime continuum constants.
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.
The Planck time is also calculated from the gravitational constant, the speed of light and Planck's constant in such a way that moving at one Planck length per one Planck time would be equal to the speed of light.
Quantum theory began in the early 1900s with the investigations by Max Planck, who determined that energy (light, radiation, heat) on the atomic level is emitted not in an infinitely divisible range of values but in discrete packets, called quanta (singular quantum), the value of which is called h or Planck's constant. Energy comes in "bits"; it is not a continuum.
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.