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Revision as of 06:09, 27 October 2001 by Josh Grosse (talk | contribs)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Photons are energy packets of electromagnetic radiation, usually given the symbol γ (the third Greek letter, gamma). They can be produced in a variety of ways, including emission from electrons as they change energy states or orbitals. Photons can also be created by nuclear transitions, particle-antiparticle annihilation or any fluctuations in an electromagnetic field which gives rise to electromagnetic radiation.
In a vacuum, photons move at the speed of light, around 3x10 meters per second. As photons move through media, they will slow down at rates dependant on their frequency, refracting the light, and causing light of different frequencies and colours to separate into a spectrum.
Photons are believed to be fundamental particles, have a definite finite energy at the speed of light, but zero invariant mass. Even so, under relativity they are affected by gravity.
See particle physics, optics and spectroscopy
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