photon

UK/ˈfəʊtɒn/US/ˈfəʊtɒn/

nounB2+Occasional — familiar, but not everyday · #10,435 of 15,258leans written

Other forms: photons

A photon is the smallest possible packet of light. A single photon, photon energy, photon detector.

Light comes in whole ones and never in halves, which is the discovery that started quantum mechanics. A photon has no mass and always travels at the speed of light, and a detector sensitive enough can register one at a time.

Definitions of photon

1nounphotonThe smallest possible packet of light.B2+
“When a photon hits the solar panel, it knocks an electron loose and creates a current.”

photon is a particle.

Where it comes from

From Greek phos, light, plus -on. Gilbert Lewis gave it the modern sense in 1926.

From photo- + -on. coined by Leonard Troland in 1916 as a unit of light hitting the retina, and later popularized in a more modern sense by Gilbert N. Lewis, with the term gaining acceptance in the physics community by the late 1920s.

Etymology from Wiktionary, CC BY-SA

Practise this word

photon in the wild

Longer-wavelength radiation such as visible light is non-ionizing; the photons do not have sufficient energy to ionize atoms.
Electromagnetic spectrum
The photon belongs to the class of boson particles.
Photon
The modern photon concept originated during the first two decades of the 20th century with the work of Albert Einstein, who built upon the research of Max Planck.
Photon
Compton scattering (or the Compton effect) is the quantum theory of scattering of a high-frequency photon through an interaction with a charged particle, usually an electron.
Compton scattering
Specifically, when the photon interacts with a loosely bound electron, it releases the electron from an outer valence shell of an atom or molecule.
Compton scattering

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From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.

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