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 As the electrons return to their normal state, the excess energy is released from the atom as a photon of light. Stephen J. Beard, USA TODAY, 18 May 2024 And the dye will then absorb the photons, excite electrons that are injected into the titanium dioxide layer and then collected by the anode and then conducted out to the cable. IEEE Spectrum, 15 May 2024 See all Example Sentences for photon 

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 29 May. 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

More from Merriam-Webster on photon

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