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The photon has no electric charge, [17] [18] is generally considered to have zero rest mass [19] and is a stable particle. The experimental upper limit on the photon mass [ 20 ] [ 21 ] is very small, on the order of 10 −50 kg; its lifetime would be more than 10 18 years. [ 22 ]
Virtual photons can have a range of polarizations, which can be described as the orientation of the electric and magnetic fields that make up the photon. The polarization of a virtual photon is determined by the direction of its momentum and its interaction with the charges that emit or absorb it.
Photon energy is the energy carried by a single photon. The amount of energy is directly proportional to the photon's electromagnetic frequency and thus, equivalently, is inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. Equivalently, the longer the photon's wavelength, the lower its energy.
Photoinduced charge separation is the process of an electron in an atom or molecule, being excited to a higher energy level by the absorption of a photon and then leaving the atom or molecule to free space, or to a nearby electron acceptor.
The energy given to the electron by the photon "excites" it into the conduction band where it is free to move around within the semiconductor. The network of covalent bonds that the electron was previously a part of now has one fewer electron. This is known as a hole, and it has positive charge.
The photon must have higher energy than the sum of the rest mass energies of an electron and positron (2 × 511 keV = 1.022 MeV, resulting in a photon wavelength of 1.2132 pm) for the production to occur. (Thus, pair production does not occur in medical X-ray imaging because these X-rays only contain ~ 150 keV.)
No real particle that is a Weyl fermion has been found to exist, and there is no compelling theoretical reason that requires them to exist. Neutrinos were originally thought to be massless – and possibly. However, because neutrinos change flavour as they travel, at least two of the types of neutrinos must have mass (and cannot be Weyl ...
A Feynman diagram (box diagram) for photon–photon scattering: one photon scatters from the transient vacuum charge fluctuations of the other. Two-photon physics, also called gamma–gamma physics, is a branch of particle physics that describes the interactions between two photons. Normally, beams of light pass through each other unperturbed.