quantum
American Heritage Dictionary:
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quan·tum
(kwŏn'təm) 
n., pl., -ta (-tə).
Relating to or based upon quantum mechanics.
n., pl., -ta (-tə).
- A quantity or amount.
- A specified portion.
- Something that can be counted or measured.
- Physics.
- The smallest amount of a physical quantity that can exist independently, especially a discrete quantity of electromagnetic radiation.
- This amount of energy regarded as a unit.
Relating to or based upon quantum mechanics.
[Latin, from neuter of quantus, how great. See quantity.]
Wiley Book of Astronomy:
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quantum
A discrete quantity of energy hv associated with a wave of frequency v. It is the smallest amount of energy that can be absorbed or radiated by matter at that frequency.
Britannica Concise Encyclopedia:
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quantum
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. quantum mechanics.
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A term characterizing an excitation in a wave or field, connoting fundamental particlelike properties such as energy or mass, momentum, and angular momentum for this excitation. In general, any field or wave equation that is quantized, including systems already treated in quantum mechanics that are second-quantized, leads to a particle interpretation for the excitations which are called quanta of the field. This term historically was first applied to indivisible amounts of electromagnetic, or light, energy usually referred to as photons. The photon, or quantum of the electromagnetic field, is a massless particle, best interpreted as such by quantizing Maxwell's equations. Analogously, the electron can be said to be the quantum of the Dirac field through second quantization of the Dirac equation, which also leads to the prediction of the existence of the positron as another quantum of this field with the same mass but with a charge opposite to that of the electron. In similar fashion, quantization of the gravitational field equations suggests the existence of the graviton. The pi meson or pion was theoretically predicted as the quantum of the nuclear force field. Another quantum is the quantized lattice vibration, or phonon, which can be interpreted as a quantized sound wave since it travels through a quantum solid or fluid, or through nuclear matter, in the same manner as sound goes through air.
The use of quantum as an adjective (quantum mechanics, quantum electrodynamics) implies that the particular subject is to be treated according to the modern rules that have evolved for quantized systems. See also Elementary particle; Gravitation; Graviton; Maxwell's equations; Meson; Phonon; Photon; Quantum electrodynamics; Quantum field theory; Quantum mechanics.
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quantum
Houghton Mifflin Guide to Science & Technology:
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The quantum
One of the most important tools of science had its start in 1665 or 1666 when young Isaac Newton observed that a prism demonstrates that white light is a mixture of the colors of the rainbow. Although scientists realized earlier that the rainbow is formed when light is broken into different colors (the spectrum), Newton was the first to make a thorough study of the subject. Later, other scientists investigated this effect for light produced by heating different elements; from this investigation we learned of the composition of the stars. It is well known that study of the spectrum reveals the composition of a heated body or gas. Much less well known is that this study also reveals much about the atom.
The spectrum not only appears in the rainbow, it is hidden in another effect. An observation that must have been made in antiquity is that as iron is heated to forge it, it first becomes dull red, then brighter red, and gradually white. Other solid materials that do not burn behave much the same way. After formulation of the electromagnetic theory of light, theorists tried to explain this phenomenon from first principles. It was apparent that longer wavelengths appear at moderate temperatures. As temperatures rise, shorter and shorter wavelengths are emitted. When the material becomes white hot, all the wavelengths are represented. Studies of even hotter bodies -- stars -- showed that in the next stage the longer wavelengths drop out, so that the color gradually moves toward the blue part of the spectrum.
Efforts to make theoretical sense of the way the spectrum gradually appears and disappears were at first unsuccessful. For one thing, theory suggested that a perfectly black body -- one that absorbs every wavelength of electromagnetic radiation equally well -- would, upon heating, radiate every wavelength equally well. Experiments with simulated black bodies, however, showed that they behave in the same way that iron does when it is heated. In the 1890s Wilhelm Wien and Lord Rayleigh each tried to find a formula to explain these phenomena, but each failed in a different way. Wien's formula worked near the blue end of the spectrum and above, but failed for long wavelengths. Rayleigh's formula was just the opposite, good for long wavelengths and not for short.
In 1900 Max Planck found an explanation that worked for all wavelengths, but little attention was paid to it. Planck made the assumption -- which seemed quite odd at the time, even to Planck -- that electromagnetic radiation could only be emitted in packets of a definite size, which he called quanta. People took notice of Planck's quantum only when Einstein, in 1905, used the idea to explain the photoelectric effect, to reconcile theory and experiment for heat, and to account for the propagation of light without relying on an "ether." It appeared that Planck's quanta went beyond theory and had a physical reality.
By 1911 Ernest Rutherford had established that the atom has a positive nucleus surrounded by orbiting electrons. Like the black-body problem, however, the theory of the atom did not match experiment. Electrons orbiting a nucleus should give off radiation constantly, resulting in the electron falling into the nucleus. But atoms do not give off that kind of energy and they are usually quite stable.
Niels Bohr turned to Planck's quantum to salvage the theory. The size of the quantum, based on a pure number called Planck's constant, could be calculated. Starting in 1913, Bohr calculated the quantum of the simplest case, hydrogen, in which a single electron orbits a proton. He showed that experiment and theory could be reconciled by saying that the quantum restricts the electron to particular orbits. For each counting number (1, 2, 3, ...) there is one permissible orbit. For a given electron, the orbit it was in could be assigned that number, called its quantum number. Bohr based his calculations on the lines that form the spectrum of hydrogen gas (when a pure gas is heated, the spectrum consists of discontinuous lines, not a full rainbow). Bohr explained the lines by saying the light is emitted when the electron changes from a higher quantum number to a lower one. Hydrogen does not display a continuous spectrum because the electron moves from orbit to orbit in "quantum jumps." More complex atoms were beyond direct calculations, but approximations indicated that the same approach was correct.
But there were minor complications. Bohr's model explained the large lines in the spectrum, but these lines are broken into smaller lines, called the fine structure of the spectrum. In 1915 Arnold Sommerfeld introduced a second quantum number to explain the fine structure. This was based on the idea that orbits allowed to electrons are ellipses, not circles. Next, it was observed that since the spectrum is affected by a magnet -- the Zeeman effect -- there needs to be a third quantum number to account for the magnetic state of the electron. Finally, in 1925 George Uhlenbeck and Samuel Goudsmit found that electrons spin, necessitating yet another quantum number. Each number is an integer that describes the specific state of the electron. If you know that the numbers are, say, 3, 1, 1, 2, then you have a precise description of the electron in its orbit.
The discovery of spin was a major breakthrough, resulting in the rapid development of what is now known as the quantum theory. In 1925 Wolfgang Pauli determined that four quantum numbers is just right. Everything known about an electron in an atom can be reduced to the four numbers. Furthermore, no two electrons in an atom can have the same numbers. This Pauli exclusion principle, as it became known, accounts for how electrons are arranged in all atoms and tells why sulfur has different properties than tin.
About the same time, Werner Heisenberg found that arrays of quantum numbers could be used to calculate lines in the spectrum. This method of calculation is called the Heisenberg matrix mechanics.
Earlier, Louis de Broglie had proposed that every particle has a wave associated with it. Erwin Schrödinger used de Broglie's idea to calculate the spectral lines. Later it was shown that the Heisenberg matrix mechanics and the Schrödinger wave equation are equivalent.
In 1927 Heisenberg put forward the idea that it is theoretically impossible to determine the position and the momentum of an electron at the same time. The greater the degree of accuracy about one quantity the less the accuracy of the other. This uncertainty principle, as it is known, was later extended to other particles and other quantities. Max Born suggested that the Schrödinger equation could be interpreted as giving the probability that an electron is located in a particular orbit. This interpretation is still the most common in quantum theory.
Although Schrödinger's wave equation gives good results, they are not perfect. The wave equation does not take spin or the theory of relativity into effect. In 1928 Paul Dirac revised the equation to include spin and relativity. Dirac's theory was important because it revealed for the first time the existence of antimatter, but the mathematics is so complicated that physicists still use the Schrödinger wave equation. Dirac's theory essentially completed classical quantum theory.
After World War II, physicists developed quantum electrodynamics, a method of calculating the behavior of electrons and other particles that is even more precise than classical quantum theory.
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Saunders Veterinary Dictionary:
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quantum
Pl. quanta [L.] an elemental unit of energy; the amount emitted or absorbed at each step when energy is emitted or absorbed by atoms or molecules.
- q. theory — radiation and absorption of energy occur in quantities (quanta) which vary in size with the frequency of the radiation.
Mosby's Dental Dictionary:
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quantum
n
A discrete unit of electromagnetic energy or of an x-ray. A quantity becomes quantized when its magnitude is restricted to a discrete set of values as opposed to a continuous set of values.
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categories related to 'quantum'
- Principles of Mechanics, Waves, and Measurement - quantum: discrete, indivisible, and elemental unit of energy that emits or absorbs waves
- Substances, Particles, and Atomic Architecture - quantum: minimum amount by which certain properties of a system, such as energy or angular momentum, can change
- Constants, Theories, and Values - quantum: minimum amount by which certain properties of a system can change
See crossword solutions for the clue Wikipedia on Answers.com:
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Quantum
For other uses, see Quantum (disambiguation).
In physics, a quantum (plural: quanta) is the minimum amount of any physical entity involved in an interaction. Behind this, one finds the fundamental notion that a physical property may be "quantized," referred to as "the hypothesis of quantization".[1] This means that the magnitude can take on only certain discrete values. There is a related term of quantum number. An example of an entity that is quantized is the energy transfer of elementary particles of matter (called fermions) and of photons and other bosons.[clarification needed]
A photon is a single quantum of light, and is referred to as a "light quantum". The energy of an electron bound to an atom (at rest) is said to be quantized, which results in the stability of atoms, and of matter in general.
As incorporated into the theory of quantum mechanics, this is regarded by physicists as part of the fundamental framework for understanding and describing nature at the infinitesimal level.
Normally quanta are considered to be discrete packets with energy stored in them. Max Planck considered these quanta to be particles that can change their form (meaning that they can be absorbed and released). This phenomenon can be observed in the case of black body radiation, when it is being heated and cooled.
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Etymology and discovery
The word "quantum" comes from the Latin "quantus," for "how much." "Quanta" meaning short for "quanta of electricity" (or electron) was used in a 1902 article on the photoelectric effect by Philipp Lenard, who credited Hermann von Helmholtz for using the word in the area of electricity. However, the word quantum in general was well known before 1900.[2] It was often used by physicians, such as the term quantum satis. Both Helmholtz and Julius von Mayer were physicians as well as physicists. Helmholtz used quantum with reference to heat in his article [3] on Mayer's work, and indeed, the word quantum can be found in the formulation of the first law of thermodynamics by Mayer in his letter [4] dated July 24, 1841. Max Planck used "quanta" to mean "quanta of matter and electricity",[5] gas, and heat.[6] In 1905, in response to Planck's work and the experimental work of Lenard, who explained his results by using the term "quanta of electricity", Albert Einstein suggested that radiation existed in spatially localized packets which he called "quanta of light" ("Lichtquanta").[7]
The concept of quantization of radiation was discovered in 1900 by Max Planck, who had been trying to understand the emission of radiation from heated objects, known as black body radiation. By assuming that energy can only be absorbed or released in tiny, differential, discrete packets he called "bundles" or "energy elements",[8] Planck accounted for the fact that certain objects change colour when heated.[9] On December 14, 1900, Planck reported his revolutionary findings to the German Physical Society and introduced the idea of quantization for the first time as a part of his research on black body radiation.[10] As a result of his experiments, Planck deduced the numerical value of h, known as the Planck constant, and could also report a more precise value for the Avogadro-Loschmidt number, the number of real molecules in a mole and the unit of electrical charge, to the German Physical Society. After his theory was validated, Planck was awarded the Nobel Prize in Physics in 1918 for his discovery.
Beyond electromagnetic radiation
While quantization was first discovered in electromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons.[11] In the attempt to bring experiment into agreement with theory, Max Planck postulated that electromagnetic energy is absorbed or emitted in discrete packets, or quanta.[12]
See also
- Basic concepts of quantum mechanics
- Elementary particle
- Graviton
- Introduction to quantum mechanics
- Magnetic flux quantum
- Photon
- Photon polarization
- Quantization (physics)
- Quantum cellular automata
- Quantum channel
- Quantum coherence
- Quantum chromodynamics
- Quantum computer
- Quantum cryptography
- Quantum dot
- Quantum electronics
- Quantum entanglement
- Quantum immortality
- Quantum lithography
- Quantum mechanics
- Quantum number
- Quantum sensor
- Quantum state
- Subatomic particle
References
- ^ Wiener, N. (1966). Differential Space, Quantum Systems, and Prediction. Cambridge: The Massachusetts Institute of Technology Press
- ^ E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
- ^ E. Helmholtz, Robert Mayer's Priorität [1] (German)
- ^ Herrmann,A. Weltreich der Physik, GNT-Verlag (1991) [2] (German)
- ^ Planck, M. (1901). "Ueber die Elementarquanta der Materie und der Elektricität". Annalen der Physik 309 (3): 564–566. Bibcode 1901AnP...309..564P. doi:10.1002/andp.19013090311. (German)
- ^ Planck, Max (1883). "Ueber das thermodynamische Gleichgewicht von Gasgemengen". Annalen der Physik 255 (6): 358. Bibcode 1883AnP...255..358P. doi:10.1002/andp.18832550612. (German)
- ^ Einstein, A. (1905). "Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt". Annalen der Physik 17 (6): 132–148. Bibcode 1905AnP...322..132E. doi:10.1002/andp.19053220607. http://www.physik.uni-augsburg.de/annalen/history/einstein-papers/1905_17_132-148.pdf. (German). A partial English translation is available from Wikisource.
- ^ Max Planck (1901). "Ueber das Gesetz der Energieverteilung im Normalspectrum (On the Law of Distribution of Energy in the Normal Spectrum)". Annalen der Physik 309 (3): 553. Bibcode 1901AnP...309..553P. doi:10.1002/andp.19013090310. Archived from the original on 2008-04-18. http://web.archive.org/web/20080418002757/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Planck-1901/Planck-1901.html.
- ^ Brown, T., LeMay, H., Bursten, B. (2008). Chemistry: The Central Science Upper Saddle River, NJ: Pearson Education ISBN 0-13-600617-5
- ^ Klein, Martin J. (1961). "Max Planck and the beginnings of the quantum theory". Archive for History of Exact Sciences 1 (5): 459. doi:10.1007/BF00327765.
- ^ Melville, K. (2005, February 11). Real-World Quantum Effects Demonstrated
- ^ Modern Applied Physics-Tippens third edition; McGraw-Hill.
Further reading
- B. Hoffmann, The Strange Story of the Quantum, Pelican 1963.
- Lucretius, On the Nature of the Universe, transl. from the Latin by R.E. Latham, Penguin Books Ltd., Harmondsworth 1951. There are, of course, many translations, and the translation's title varies. Some put emphasis on how things work, others on what things are found in nature.
- J. Mehra and H. Rechenberg, The Historical Development of Quantum Theory, Vol.1, Part 1, Springer-Verlag New York Inc., New York 1982.
- M. Planck, A Survey of Physical Theory, transl. by R. Jones and D.H. Williams, Methuen & Co., Ltd., London 1925 (Dover editions 1960 and 1993) including the Nobel lecture.
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Translations:
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Quantum
idioms:
- quantum jump kvantespring
- quantum leap kvantespring
- quantum mechanics kvantemekanik
- quantum number kvantetal, varenummer
- quantum theory kvanteteori
Français (French)
n. - quantum, quanta (plur)
adj. - quantique
idioms:
- quantum jump (Phys) saut quantique
- quantum leap (Phys) saut quantique, (fig) saut prodigieux
- quantum mechanics mécanique quantique
- quantum number chiffre quantique
- quantum theory théorie des quanta
Deutsch (German)
n. - Quantum, Menge, (An)teil, (phys.) Quant
adj. - groß, bedeutend
idioms:
- quantum jump Quantensprung
- quantum leap Quantensprung
- quantum mechanics Quantenmechanik
- quantum number Quantenzahl
- quantum theory Quantentheorie
Ελληνική (Greek)
n. - ποσότητα, ποσοστό, (φυσ.) κβάντο
adj. - (φυσ.) κβαντικός
idioms:
- quantum jump σημαντικό άλμα
- quantum leap σημαντικό άλμα
- quantum mechanics (φυσ.) κβαντομηχανική
- quantum number (φυσ.) κβαντικός αριθμός
- quantum theory (φυσ.) κβαντική θεωρία
idioms:
- quantum leap/jump salto quantico, balzo quantico
- quantum mechanics meccanica quantistica
- quantum number numero quantico
- quantum theory teoria dei quanti
Português (Portuguese)
n. - quantidade (f), fração (f), quanto (m) (Fís.)
adj. - quântico
idioms:
- quantum leap/jump transição/salto quântico
- quantum mechanics mecânica quântica
- quantum number número quântico
- quantum theory teoria dos quanta
Русский (Russian)
количество, величина
idioms:
- quantum leap/jump квантовый скачок
- quantum mechanics квантовая механика
- quantum number квантовое число
- quantum theory квантовая теория
Español (Spanish)
n. - cantidad, cuanto
idioms:
- quantum jump gran salto, gran cambio
- quantum leap gran salto, gran cambio
- quantum mechanics mecánica cuántica
- quantum number número cuántico
- quantum theory teoría cuántica
Svenska (Swedish)
n. - kvantum, mängd, del, lott, kvant, kvantum (fys.)
adj. - kvant-
中文（简体）(Chinese (Simplified))
分配量, 量, 额
idioms:
- quantum jump 量子跳变, 突然的改变, 大飞跃
- quantum leap 量子跃进, 突然的改变, 大飞跃
- quantum mechanics 量子力学
- quantum number 量子数
- quantum theory 量子论
中文（繁體）(Chinese (Traditional))
n. - 分配量, 量, 額
idioms:
- quantum jump 量子跳變, 突然的改變, 大飛躍
- quantum leap 量子躍進, 突然的改變, 大飛躍
- quantum mechanics 量子力學
- quantum number 量子數
- quantum theory 量子論
日本語 (Japanese)
n. - 量, 量子, 数量
adj. - 画期的な
idioms:
- quantum leap/jump 大きな飛躍
- quantum mechanics 量子力学
- quantum number 量子数
- quantum theory 量子論
العربيه (Arabic)
(الاسم) كميه, جزء (صفه) ذو أهميه بالغه
עברית (Hebrew)
n. - כמות, מנה, חלק, קוונט, כמות אנרגיה העומדת ביחס ישר למידת הקרינה ולתכיפותה
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