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A photon (light particle) is the quantum of energy as a form of electromagnetic radiation.



A photon is the carrier of electromagnetism. Photons have spin 1 and are thus gauge bosons.

G a u g e   b o s o n



Light particles move at the speed of light c. From special relativity it follows that a particle with a rest mass greater than 0 never can reach the speed of light. A light particle has no rest mass, and is therefor a massless particle.



A light particle does not desintegrate and is therefore completely stable. According to the special theory of relativity the local time of a light particle stands still, so a light particle does not get the time to fall apart.



A photon can be polarized horizontally or vertically. Until the polarization is measured, the photon is in a superposition of these two states, and we can write this as

|ψ⟩ = α |H⟩ + β |V

in which α and β are complex probability amplitudes. The probability that you measure a photon with status |H is |α|2 and that you measure the status |V is |β|2, because it applies

|α|2 + |β|2 = 1


Additional information

The concept of the photon was developed by Albert Einstein in 1905. The name of "photon" is attributed to Gilbert N. Lewis (1926).


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