photon

noun

pho·ton | \ˈfō-ˌtän

Definition of photon

1 : a quantum of electromagnetic radiation Should a substance happen to have a lot of electrons in a higher level, and a lower level is mostly empty …, then a photon can cause an electron to transfer from a higher state to a lower one. This change releases energy and creates a new photon, in addition to the one which caused the transfer. This photon can in turn induce more electrons to fall to a lower state.— Robert Gilmore

2 dated : troland

Other Words from photon Science and the Photon More Example Sentences Learn More about photon

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Science and the Photon

It was Albert Einstein who first theorized that the energy in a light beam exists in small bits or particles, and scientists today know that light sometimes behaves like a wave (somewhat like sound or water) and sometimes like a stream of particles. The energies of photons range from high-energy gamma rays and X-rays down to low-energy infrared and radio waves, though all travel at the same speed. The amazing power of lasers is the result of a concentration of photons that have been made to travel together in order to hit their target at the same time.

Examples of photon in a Sentence

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These photons started out with short radio wavelengths, but over their more than 13-billion-year journey to Earth, the universe's expansion stretched them out to long wavelengths, or low megahertz frequencies. — Daniel Clery, Science | AAAS, "China’s moon mission will probe cosmic dark ages," 16 May 2018 In fact, neutrinos are the second most ubiquitous particles, second only to the cosmic microwave background photons left over from the Big Bang. — Smithsonian, "Scientists Explain The Thrill of Detecting a Neutrino From a Far-Off Galaxy," 12 July 2018 The defects can take and store quantum information in the form of electrons for relatively long periods of time and link it efficiently to photons. — Fox News, "Scientists are using diamonds to send secret messages," 6 July 2018 Just like a photon of light behaves like both a particle and a wave, this blob also has wavelike properties, where one part can actually interfere with another part, to produce ripples in itself like waves colliding in a pond. — Sophia Chen, WIRED, "The Quest to Make Super Cold Quantum Blobs in Space," 25 June 2018 High-energy light from distant sources rarely makes it to Earth, because photons are so reactive they get lost along the way. — Author: Sarah Kaplan, Anchorage Daily News, "In a cosmic first, scientists detect ‘ghost particles’ from a distant galaxy," 12 July 2018 High-energy light from distant sources rarely makes it to Earth, because photons are so reactive they get lost along the way. — Sarah Kaplan, chicagotribune.com, "In a cosmic first, scientists detect 'ghost particles' from a distant galaxy," 12 July 2018 Both were designed to catch photons from planets around other stars, unlike most techniques for studying exoplanets that rely on more indirect signatures. — Joshua Sokol, WIRED, "These Spinning Disks of Gas and Dust Reveal How Planets Get Made," 28 May 2018 And the world awaits the words, for the same reason that astronomers search the heavens for the precious photons from remote galaxies, or that Newton spent his last years consumed by Biblical prophecy: Hawking is trying to read the mind of God. — Jerry Adler, Newsweek, "Stephen Hawking, Master of the Universe: Our 1988 Cover Story on the Legendary Physicist," 14 Mar. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'photon.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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15 Oct 2018

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The first known use of photon was in 1916

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More Definitions for photon

photon

noun

English Language Learners Definition of photon

physics : a tiny particle of light or electromagnetic radiation

See the full definition for photon in the English Language Learners Dictionary

photon

noun

pho·ton | \ˈfō-ˌtän

Medical Definition of photon

1 : a unit of intensity of light at the retina equal to the illumination received per square millimeter of a pupillary area from a surface having a brightness of one candela per square meter

— called also troland

2 : a quantum of electromagnetic radiation