quantum


quantum
/kwon"teuhm/, n., pl. quanta /-teuh/, adj.
n.
1. quantity or amount: the least quantum of evidence.
2. a particular amount.
3. a share or portion.
4. a large quantity; bulk.
5. Physics.
a. the smallest quantity of radiant energy, equal to Planck's constant times the frequency of the associated radiation.
b. the fundamental unit of a quantized physical magnitude, as angular momentum.
adj.
6. sudden and significant: a quantum increase in productivity.
[1610-20; n. use of neut. of L quantus how much]

* * *

I
In physics, a discrete natural unit, or packet, of energy, charge, angular momentum, or other physical property.

Light, for example, which appears in some respects as a continuous electromagnetic wave, on the submicroscopic level is emitted and absorbed in discrete amounts, or quanta; for light of a given wavelength, the magnitude of all the quanta emitted or absorbed is the same in both energy and momentum. These particlelike packets of light are called photons, a term also applicable to quanta of other forms of electromagnetic energy such as X rays and gamma rays. Submicroscopic mechanical vibrations in the layers of atoms comprising crystals also give up or take on energy and momentum in quanta called phonons. See also quantum mechanics.
II
(as used in expressions)

* * *

      in physics, discrete natural unit, or packet, of energy, charge, angular momentum, or other physical property. Light, for example, appearing in some respects as a continuous electromagnetic wave, on the submicroscopic level is emitted and absorbed in discrete amounts, or quanta; and for light of a given wavelength, the magnitude of all the quanta emitted or absorbed is the same in both energy and momentum. These particle-like packets of light are called photons (photon), a term also applicable to quanta of other forms of electromagnetic energy such as X rays and gamma rays. Submicroscopic mechanical vibrations in the layers of atoms comprising crystals also give up or take on energy and momentum in quanta called phonons (phonon).

      All phenomena in submicroscopic systems (the realm of quantum mechanics) exhibit quantization: observable quantities are restricted to a natural set of discrete values. When the values are multiples of a constant least amount, that amount is referred to as a quantum of the observable. Thus Planck's constant h is the quantum of action, and ℏ (i.e., h/2π) is the quantum of angular momentum, or spin.

* * *


Universalium. 2010.

Look at other dictionaries:

  • quantum — plur. quanta [ k(w)ɑ̃tɔm, k(w)ɑ̃ta ] n. m. • 1624; mot lat. « combien » 1 ♦ (par l angl.) Philos. Quantité déterminée. ♢ Dr., admin. Montant (d une amende, d une pension, d une part). 2 ♦ (1911; all …   Encyclopédie Universelle

  • Quantum — Quan tum, n.; pl. {Quanta}. [L., neuter of quantus how great, how much. See {Quantity},] 1. Quantity; amount. Without authenticating . . . the quantum of the charges. Burke. [1913 Webster] 2. (Math.) A definite portion of a manifoldness, limited… …   The Collaborative International Dictionary of English

  • quantum — (n.) 1610s, one s share or portion, from L. quantum how much, neuter singular of quantus how great (see QUANTITY (Cf. quantity)). Introduced in physics by Max Planck, 1900; reinforced by Einstein, 1905. Quantum theory is from 1912; quantum… …   Etymology dictionary

  • Quantum 2 — Localisation Coordonnées …   Wikipédia en Français

  • Quantum — (von lateinisch für „wie viel“, „wie groß“) ist: ein umgangssprachlicher Begriff mit der Bedeutung eine bestimmte Menge oder eine bestimmte Anzahl eine ehemalige Automobilmarke; siehe Quantum (Automarke) ein US Unternehmen, das… …   Deutsch Wikipedia

  • quantum — index bulk, proportion, quantity, quota Burton s Legal Thesaurus. William C. Burton. 2006 …   Law dictionary

  • quantum — UK US /ˈkwɒntəm/ noun [C, usually singular] FORMAL ► an amount of something: quantum of sth »Earnings depend on the quantum of work done by you. »During this period, the quantum of oil production increased to 16.10 million barrels from 15.84… …   Financial and business terms

  • Quantum — Sn erw. fremd. Erkennbar fremd (16. Jh.) Entlehnung. Neutralform von l. quantus wieviel . Wird aus der Wissenschaftssprache und Kaufmannssprache übernommen und nicht eingedeutscht.    Ebenso nndl. quantum, ne. quantum, nfrz. quantum, nschw.… …   Etymologisches Wörterbuch der deutschen sprache

  • quantum — |quantum| s. m. 1. Quantidade ou soma que não se designa. 2. Quantidade referente a cada um numa repartição. 3. Montante de uma indenização. 4.  [Física] Quantidade mínima de energia que pode ser emitida, propagada ou absorvida. [A teoria dos… …   Dicionário da Língua Portuguesa

  • Quantum — Quantum: Der Ausdruck für »Menge, Anzahl; Anteil; ‹bestimmtes› Maß« wurde im 17. Jh. in der Kaufmannssprache aus lat. quantum, dem Neutrum von lat. quantus »wie groß, wie viel; so groß wie« übernommen. – Dazu: Quantität »Menge, Masse, Anzahl; (in …   Das Herkunftswörterbuch

  • quantum — [kwän′təm] n. pl. quanta [kwän′tə] [L, neut. sing. of quantus, how much: see QUANTITY] 1. quantity, or amount 2. a specified quantity; portion 3. in the quantum theory, a (or the) fixed, elemental unit, as of energy, angular momentum, etc …   English World dictionary


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.