pho·​ton | \ ˈfō-ˌtän How to pronounce photon (audio) \

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

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Other Words from photon

photonic \ fō-​ˈtä-​nik How to pronounce photonic (audio) \ adjective

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

Recent Examples on the Web Then the extraordinary rules of quantum theory would kick in: the electron would, at once, both absorb and not absorb a microwave photon, creating a quantum superposition of the diamond. Tim Folger, Scientific American, "Tiny Gravitational-Wave Detector Could Search Anywhere in the Sky," 30 June 2020 One of them arose from splitting a single photon between two different paths. Dhananjay Khadilkar, Scientific American, "‘Hybrid’ Quantum Networking Demonstrated for First Time," 2 July 2020 In particular, Lin and Kozaczuk calculated that low-mass dark matter would create plasmons at about one ten-thousandth the rate of directly producing an electron or photon. Daniel Garisto, Scientific American, "Direct Proof of Dark Matter May Lurk at Low-Energy Frontiers," 9 June 2020 One photon of sunlight too much, and it’d wilt like old lettuce. Paul Cappiello, The Courier-Journal, "Everything old is new again, especially for this vibrant, colorful and hearty garden plant," 5 June 2020 Second to photons, which compose electromagnetic radiation, neutrinos are the most plentiful subatomic particles in the universe, famed for their ability to waft through ordinary matter like ghosts through a wall. Dennis Overbye, New York Times, "Why the Big Bang Produced Something Rather Than Nothing," 15 Apr. 2020 The travel time of the photons reveals the surface height—and any changes—to within millimeters. Paul Voosen, Science | AAAS, "Ice-tracking space laser could also map sea floor and monitor health of coral reefs," 14 Apr. 2020 As the name suggests, SPADs are sensitive enough to detect a single photon. Timothy B. Lee, Ars Technica, "Most lidars today have between 1 and 128 lasers—this one has 11,000," 16 Jan. 2020 In these protocols, two parties exchange information encoded in individual photons of light, perhaps relayed by a satellite in orbit. Sophia Chen, Wired, "Physicists Clear the Air With a Sweet Frickin' Laser Beam," 29 Apr. 2020

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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First Known Use of photon

1916, in the meaning defined at sense 2

History and Etymology for photon

phot- + -on entry 2

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Time Traveler for photon

Time Traveler

The first known use of photon was in 1916

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Statistics for photon

Last Updated

1 Aug 2020

Cite this Entry

“Photon.” Dictionary, Merriam-Webster, Accessed 8 Aug. 2020.

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More Definitions for photon


How to pronounce photon (audio)

English Language Learners Definition of photon

physics : a tiny particle of light or electromagnetic radiation


pho·​ton | \ ˈfō-ˌtän How to pronounce photon (audio) \

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

More from Merriam-Webster on photon

Rhyming Dictionary: Words that rhyme with photon Encyclopedia article about photon

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