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

Another thing photons are is weird—very, very weird. —Phil Plait, Scientific American, 5 July 2024

However, quantum mechanics dictates that each photon will be both transmitted and reflected. —science.org, 10 June 2024

There is a field for each of the particles in nature, from common particles such as electrons and photons to their more exotic cousins such as muons and gluons. —Luke Caldwell, Scientific American, 1 Feb. 2024

The precision melting is accomplished with femtosecond lasers, which pack a tremendous number of photons into a very short time scale--about one millionth of one billionth of a second. —IEEE Spectrum, 9 May 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