photon

noun

pho·​ton ˈfō-ˌtän How to pronounce photon (audio)
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
photonic adjective

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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

Recent Examples on the Web This is a star that has carved a bubble in these clouds by emitting energetic ultraviolet photons, a figurative candle in the darkness. Eric Berger, Ars Technica, 12 July 2023 But on a grassland, the sparse vegetation might let more photons in. Matt Simon, WIRED, 9 Oct. 2023 Some processes in physics happen in the blink of an eye while others happen in the blink of a photon. Daniel Garisto, Scientific American, 3 Oct. 2023 The researchers are also working to increase the quantity of emitted photons and to improve their quality and speed of emission. IEEE Spectrum, 10 Jan. 2024 The instrument will lock onto the beam and download the message, using a camera that counts the light particles, or photons, before relaying it back down at a high rate to the 200-inch Hale telescope on Mount Palomar near San Diego, where it can be compared for accuracy to the original. John Johnson Jr., Discover Magazine, 27 Nov. 2023 Over the course of a year, Chandra stared at the cosmic lens for two weeks—one of its longest observation campaigns yet—and collected 19 x-ray photons coming from a galaxy called UHZ1, at a redshift of 10.1. WIRED, 5 Nov. 2023 It's very roughly described that the suit takes photons, light particles, and converts them into electrical impulses that then presumably get converted back into light on the other side. Jennifer Ouellette, Ars Technica, 17 July 2023 That’s a problem, because in traditional—that is, fluorescent—OLEDs, only the singlets emit photons, while the triplets release their energy as heat. IEEE Spectrum, 19 Dec. 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'photon.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

phot- + -on entry 2

First Known Use

1916, in the meaning defined at sense 2

Time Traveler
The first known use of photon was in 1916

Dictionary Entries Near photon

Cite this Entry

“Photon.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/photon. Accessed 19 Mar. 2024.

Kids Definition

photon

noun
pho·​ton ˈfō-ˌtän How to pronounce photon (audio)
: a tiny particle or bundle of electromagnetic radiation

Medical Definition

photon

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

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