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〔 〕 |mean_lifetime=Stable〔 |decay_particle= |electric_charge=0 〔 |color_charge= |spin=1 |num_spin_states= |parity=−1〔 |g_parity= |c_parity=−1〔 |r_parity= |condensed_symmetries=''I''(''J''''PC'')=0,1(1−−)〔 }} A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation. It is the force carrier for the electromagnetic force, even when static via virtual photons. The effects of this force are easily observable at the microscopic and at the macroscopic level, because the photon has zero rest mass; this allows long distance interactions. Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of waves and of particles. For example, a single photon may be refracted by a lens or exhibit wave interference with itself, but also act as a particle giving a definite result when its position is measured. Waves and quanta, being two observable aspects of a single phenomenon cannot have their true nature described in terms of any mechanical model. A representation of this dual property of light, which assumes certain points on the wave front to be the seat of the energy is also impossible. Thus, the quanta in a light wave cannot be spatially localized. Some defined physical parameters of a photon are listed. The modern photon concept was developed gradually by Albert Einstein in the first years of the 20th century to explain experimental observations that did not fit the classical wave model of light. In particular, the photon model accounted for the frequency dependence of light's energy, and explained the ability of matter and radiation to be in thermal equilibrium. It also accounted for anomalous observations, including the properties of black-body radiation, that other physicists, most notably Max Planck, had sought to explain using ''semiclassical models'', in which light is still described by Maxwell's equations, but the material objects that emit and absorb light do so in amounts of energy that are ''quantized'' (i.e., they change energy only by certain particular discrete amounts and cannot change energy in any arbitrary way). Although these semiclassical models contributed to the development of quantum mechanics, many further experiments starting with Compton scattering of single photons by electrons, first observed in 1923, validated Einstein's hypothesis that ''light itself'' is quantized. In 1926 the optical physicist Frithiof Wolfers and the chemist Gilbert N. Lewis coined the name ''photon'' for these particles, and after 1927, when Arthur H. Compton won the Nobel Prize for his scattering studies, most scientists accepted the validity that quanta of light have an independent existence, and the term ''photon'' for light quanta was accepted. In the Standard Model of particle physics, photons and other elementary particles are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of particles, such as charge, mass and spin, are determined by the properties of this gauge symmetry. The photon concept has led to momentous advances in experimental and theoretical physics, such as lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics. It has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Recently, photons have been studied as elements of quantum computers and for applications in optical imaging and optical communication such as quantum cryptography. ==Nomenclature== In 1900, the German physicist Max Planck was working on black-body radiation and suggested that the energy in electromagnetic waves could only be released in "packets" of energy. In his 1901 article 〔 in Annalen der Physik he called these packets "energy elements". The word ''quanta'' (singular ''quantum'') was used even before 1900 to mean particles or amounts of different quantities, including electricity. Later, in 1905, Albert Einstein went further by suggesting that electromagnetic waves could only exist in these discrete wave-packets.〔. An English translation is available from Wikisource.〕 He called such a wave-packet ''the light quantum'' (German: ''das Lichtquant'').〔Although the 1967 (Elsevier translation ) of Planck's Nobel Lecture interprets Planck's ''Lichtquant'' as "photon", the more literal 1922 translation by Hans Thacher Clarke and Ludwik Silberstein (''The origin and development of the quantum theory'' ), The Clarendon Press, 1922 (here ()) uses "light-quantum". No evidence is known that Planck himself used the term "photon" by 1926 (see also (this note )).〕 The name ''photon'' derives from the Greek word for light, ' (transliterated ''phôs''). Arthur Compton used ''photon'' in 1928, referring to Gilbert N. Lewis.〔"Discordances entre l'expérience et la théorie électromagnétique du rayonnement." In Électrons et Photons. Rapports et Discussions de Cinquième Conseil de Physique, edited by Institut International de Physique Solvay. Paris: Gauthier-Villars, pp. 55-85.〕 The same name was used earlier, by the American physicist and psychologist Leonard T. Troland, who coined the word in 1916, in 1921 by the Irish physicist John Joly, in 1924 by the French physiologist René Wurmser (1890-1993) and in 1926 by the French physicist Frithiof Wolfers (1891-1971).〔Helge Kragh: (''Photon: New light on an old name'' ). Arxiv, 2014-2-28〕 The name was suggested initially as a unit related to the illumination of the eye and the resulting sensation of light and was used later on in a physiological context. Although Wolfers's and Lewis's theories were never accepted, as they were contradicted by many experiments, the new name was adopted very soon by most physicists after Compton used it.〔〔Isaac Asimov credits Arthur Compton with defining quanta of energy as photons in 1923. and 〕 In physics, a photon is usually denoted by the symbol ''γ'' (the Greek letter gamma). This symbol for the photon probably derives from gamma rays, which were discovered in 1900 by Paul Villard,〔 〕 named by Ernest Rutherford in 1903, and shown to be a form of electromagnetic radiation in 1914 by Rutherford and Edward Andrade. In chemistry and optical engineering, photons are usually symbolized by ''hν'', the energy of a photon, where ''h'' is Planck's constant and the Greek letter ''ν'' (nu) is the photon's frequency. Much less commonly, the photon can be symbolized by ''hf'', where its frequency is denoted by ''f''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「photon」の詳細全文を読む スポンサード リンク
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