photon

noun
pho·​ton | \ ˈfō-ˌtän How to pronounce photon (audio) \

Definition of photon

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

Keep scrolling for more

Other Words from photon

photonic \ fō-​ˈtä-​nik How to pronounce photonic (audio) \ adjective

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

The process of making a photon is like setting a swing in motion. Chris Lee, Ars Technica, "Pulsars could convert dark matter into something we could see," 20 Dec. 2018 The energy of a photon gets absorbed by an electron in the material which then jumps, leaving behind a hole. Charles W. Dunnill, Scientific American, "Method of Making Oxygen from Water in Zero Gravity Raises Hope for Long-Distance Space Travel," 10 July 2018 The wavelength of the photon is dictated by the energy of the electrons and the spacing of the magnets. Chris Lee, Ars Technica, "Single-beam laser becomes multi-beam laser by kicking electrons," 5 Dec. 2018 This allows astronomers to accentuate the photons that have bounced off a disk or a planet. Joshua Sokol, WIRED, "These Spinning Disks of Gas and Dust Reveal How Planets Get Made," 28 May 2018 Our eyes have evolved to be exquisitely sensitive to these photons. Tim Folger, Discover Magazine, "How Quantum Mechanics Lets Us See, Smell and Touch," 24 Oct. 2018 Now, the photons from Alpha Centauri arrive at 112.3 years after the LHC fired—1.7 years after the signal from Earth, which is still superluminal. John Timmer, Ars Technica, "Why things can look like they’re moving faster than light," 9 Sep. 2018 Essentially, the photons from the laser pelt the atoms, nudging them in a specific direction until they are confined to specific areas inside the chamber designed to hold only a single atom. Sophia Chen, WIRED, "Chemists Orchestrate the Molecular Union of Two Single Atoms," 27 Apr. 2018 Alice has a device that generates pairs of photons. Chris Lee, Ars Technica, "Conservation of energy used to parallelize quantum key distribution," 17 Dec. 2018

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.

See More

First Known Use of photon

1916, in the meaning defined at sense 2

History and Etymology for photon

phot- + -on entry 2

Keep scrolling for more

Learn More about photon

Statistics for photon

Last Updated

16 Apr 2019

Look-up Popularity

Time Traveler for photon

The first known use of photon was in 1916

See more words from the same year

Keep scrolling for more

More Definitions for photon

photon

noun

English Language Learners Definition of photon

physics : a tiny particle of light or electromagnetic radiation

photon

noun
pho·​ton | \ ˈfō-ˌtän How to pronounce photon (audio) \

Medical Definition of photon

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

Rhyming Dictionary: Words that rhyme with photon

Britannica.com: Encyclopedia article about photon

Comments on photon

What made you want to look up photon? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

an enemy or opponent

Get Word of the Day daily email!

Test Your Vocabulary

Words from Greek and Latin Quiz

  • roman forum
  • Which of the following months comes from a Latin word for “ten”?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!