photon

noun

pho·​ton ˈfō-ˌtän 

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

fō-ˈtä-nik 

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

Additionally, these molecules cool the PV cell by acting as an optical filter that blocks the photons that would normally cause the cell to heat up and reduce efficiency. —New Atlas, 26 Sep. 2024

This motion takes too much energy to be induced by Earth’s infrared photons on their own. —Joseph Howlett, WIRED, 25 Aug. 2024

Above that energy, photons will be sparse (they may still be produced by things like processes that accelerate particles). —John Timmer, Ars Technica, 31 July 2024

The photon might have been produced by a distant quasar and the role of the double-slit screen played by a galaxy whose gravitational field will deflect the photon leftward or rightward with equal probability. —Quanta Magazine, 25 Sep. 2024

Word History

Etymology

phot- + -on entry 2

First Known Use

1916, in the meaning defined at sense 2

Kids Definition

photon

noun

pho·​ton ˈfō-ˌtän 

: a tiny particle or bundle of electromagnetic radiation

Medical Definition

photon

noun

pho·​ton ˈfō-ˌtän 

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