photon

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noun pho·ton \ˈfō-ˌtän\

Definition of photon

  1. 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. 2 dated :  troland

photonic

play \fō-ˈtä-nik\ adjective

Recent Examples of photon from the Web

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.

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.

Origin and Etymology of photon

phot- + 2-on


PHOTON Defined for English Language Learners

photon

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noun

Definition of photon for English Language Learners

  • physics : a tiny particle of light or electromagnetic radiation


Medical Dictionary

photon

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noun pho·ton \ˈfō-ˌtän\

Medical Definition of photon

  1. 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. 2:  a quantum of electromagnetic radiation


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