photon

play
noun pho·ton \ˈfō-ˌtän\

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 candle per square meter

  2. 2 :  a quantum of electromagnetic radiation

photonic

play \fō-ˈtä-nik\ adjective

Did You Know?

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


First Known Use: 1916


PHOTON Defined for English Language Learners

photon

play
noun pho·ton \ˈfō-ˌtän\

Definition of photon for English Language Learners

  • physics : a tiny particle of light or electromagnetic radiation


Medical Dictionary

photon

play
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


Learn More about photon


Seen and Heard

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 alert or lookout

Get Word of the Day daily email!

WORD GAMES

Take a 3-minute break and test your skills!

  • alphabet-magnets
  • Which is the correct spelling?
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