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Hence, conservation of momentum (or equivalently, translational invariance) requires that at least two photons are created, with zero net momentum. [ c ] [ 31 ] : 64–65 The energy of the two photons, or, equivalently, their frequency, may be determined from conservation of four-momentum .
Thus, matter can be created out of two photons. The law of conservation of energy sets a minimum photon energy required for the creation of a pair of fermions: this threshold energy must be greater than the total rest energy of the fermions created.
As energy must be conserved, for pair production to occur, the incoming energy of the photon must be above a threshold of at least the total rest mass energy of the two particles created. (As the electron is the lightest, hence, lowest mass/energy, elementary particle, it requires the least energetic photons of all possible pair-production ...
As a result, photons no longer interacted frequently with matter, the universe became transparent and the cosmic microwave background radiation was created and then structure formation took place. This is referred to as the surface of last scattering , as it corresponds to a virtual outer surface of the spherical observable universe .
In the most common case, two gamma photons are created, each with energy equal to the rest energy of the electron or positron (0.511 MeV). [2] A convenient frame of reference is that in which the system has no net linear momentum before the annihilation; thus, after collision, the gamma photons are emitted in opposite directions.
Scientists just proved that one packet of light is enough to kickstart the whole process.
The Breit–Wheeler process is the creation of an electron–positron pair following the collision of two high-energy photons (gamma photons). The nonlinear Breit–Wheeler process or multiphoton Breit–Wheeler is the creation of an electron-positron pair from the decay of a high-energy photon (gamma photon) interacting with a strong electromagnetic field such as a laser.
Photons that don’t easily interact with each other, for example, can be used in communication to offer near distortion-free transfer of information at light speed. But sometimes, we do want ...