Inphysics, aquantum (pl.:quanta) is the minimum amount of any physical entity (physical property) involved in aninteraction. The fundamental notion that a property can be "quantized" is referred to as "the hypothesis ofquantization".[1] This means that themagnitude of the physical property can take on onlydiscrete values consisting ofinteger multiples of one quantum. For example, aphoton is a single quantum oflight of a specificfrequency (or of any other form ofelectromagnetic radiation). Similarly, the energy of anelectron bound within anatom is quantized and can exist only in certain discrete values.[2] Atoms and matter in general are stable because electrons can exist only at discrete energy levels within an atom. Quantization is one of the foundations of the much broader physics ofquantum mechanics. Quantization ofenergy and its influence on how energy and matter interact (quantum electrodynamics) is part of the fundamental framework for understanding and describing nature.
Germanphysicist and 1918 Nobel Prize for Physics recipientMax Planck (1858–1947)
The modern concept of the quantum in physics originates from December 14, 1900, whenMax Planck reported hisfindings to theGerman Physical Society. He showed that modelling harmonic oscillators with discrete energy levels resolved a longstanding problem in the theory ofblackbody radiation.[3]: 15 [4] In his report, Planck did not use the termquantum in the modern sense. Instead, he used the termElementarquantum to refer to the "quantum of electricity", now known as theelementary charge. For the smallest unit of energy, he employed the termEnergieelement, "energy element", rather than calling it aquantum.[5]
Shortly afterwards, in a paper published inAnnalen der Physik,[6] Planck introduced the constanth, which he termed the "quantum ofaction" (elementares Wirkungsquantum) in 1906.[5] In this paper, Planck also reported more precise values for the elementary charge and theAvogadro–Loschmidt number, the number of molecules in onemole of substance.[7] The constanth is now known as thePlanck constant. After his theory was validated, Planck was awarded theNobel Prize in Physics for his discovery in 1918.[8]
In 1905Albert Einstein suggested thatelectromagnetic radiation exists in spatially localized packets which he called"quanta of light" (Lichtquanta).[5][9]Einstein was able to use this hypothesis to recast Planck's treatment of the blackbody problem in a form that also explained the voltages observed inPhilipp Lenard's experiments on thephotoelectric effect.[3]: 23 Shortly thereafter, the term "energy quantum" was introduced for the quantityhν.[10]
While quantization was first discovered inelectromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons.[11]In the attempt to bring theory into agreement with experiment, Max Planck postulated that electromagnetic energy is absorbed or emitted in discrete packets, or quanta.[12]
^Wiener, N. (1966).Differential Space, Quantum Systems, and Prediction. Cambridge, Massachusetts: The Massachusetts Institute of Technology Press
^Rovelli, Carlo (January 2017).Reality is not what it seems: the elementary structure of things. Translated by Carnell, Simon; Segre, Erica (1st American ed.). New York, New York: Riverhead Books. pp. 109–130.ISBN978-0-7352-1392-0.
^abBaggott, J. E. (2013).The quantum story: a history in 40 moments (Pbk ed.). Oxford [England]: Oxford University Press.ISBN978-0-19-965597-7.
^Klein, Martin J. (1961). "Max Planck and the beginnings of the quantum theory".Archive for History of Exact Sciences.1 (5):459–479.doi:10.1007/BF00327765.S2CID121189755.
Hoffmann, Banesh (1959).The Strange story of the quantum: An account for the general reader of the growth of the ideas underlying our present atomic knowledge (2 ed.). New York: Dover.ISBN978-0-486-20518-2.{{cite book}}:ISBN / Date incompatibility (help)
Mehra, Jagdish;Rechenberg, Helmut; Mehra, Jagdish; Rechenberg, Helmut (2001).The historical development of quantum theory. 4: Pt.1, the fundamental equations of quantum mechanics, 1925-1926 (1. softcover print ed.). New York Heidelberg: Springer.ISBN978-0-387-95178-2.
M. Planck,A Survey of Physical Theory, transl. by R. Jones and D.H. Williams, Methuen & Co., Limited., London 1925 (Dover edition 17 May 2003, ISBN 978-0486678672) including the Nobel lecture.
Rodney, Brooks (14 December 2010)Fields of Color: The theory that escaped Einstein. Allegra Print & Imaging. ISBN 979-8373308427
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