electron-volt

electron-volt abbr. eV, unit of energy used in atomic and nuclear physics; 1 electron-volt is the energy transferred in moving a unit charge , positive or negative and equal to that charge on the electron, through a potential difference of 1 volt. The maximum energy of a particle accelerator is usually expressed in multiples of the electron-volt, such as million electron-volts (MeV) or billion electron-volts (GeV). Because mass is a form of energy (see relativity ), the masses of elementary particles are sometimes expressed in electron-volts; e.g., the mass of the electron, the lightest particle with measurable rest mass, is 0.51 MeV/ c² , where c is the speed of light.

e·lec·tron volt (abbr.: eV) • n. Physics a unit of energy equal to the work done on an electron in accelerating it through a potential difference of one volt.

electronvolt (symbol eV) A unit of energy used in atomic and nuclear physics. It is defined as the energy acquired by an electron in falling through a potential difference of one volt. One electronvolt is equal to 1.602 × 10^-19 joule. Electronvolts are used as a measure of the energy of cosmic rays and high-energy photons. X-rays and gamma rays can have energies of 100 000 eV or more. By comparison, optical photons have energies of 2–3 eV. The rest mass of atomic particles can also be expressed in terms of electronvolts, since mass and energy are equivalent. Hence the rest mass of an electron is about 500 keV and that of protons and neutrons about 1000 MeV. Electronvolts can be converted to wavelength (λ) by the formula λ = 1239.8nm/eV.