Electronvolt as a unit of energy and mass
– An electronvolt is the amount of kinetic energy gained or lost by a single electron accelerating from rest through an electric potential difference of one volt in vacuum.
– It is equivalent to the charge of an electron in coulombs.
– The electronvolt is not an SI unit, with the joule being the SI unit of energy.
– The kilogram equivalent of 1eV/c^2 is approximately 1.78266192×10^-36 kg.
– The GeV is commonly used as a unit of mass in particle physics, where 1GeV is approximately 1.78266192×10^-27 kg.
Momentum and energy-momentum relation
– Momentum can be described in units of eV/c by dividing a particle’s kinetic energy in electronvolts by the speed of light.
– The energy-momentum relation in natural units is represented by the equation E^2 = p^2 + m0^2.
– In high-energy physics, when a relatively high energy is applied to a particle with relatively low rest mass, the change in momentum can be approximated as E ≈ p.
– Momentum units have dimensions of TLM, while energy units have dimensions of TM.
– Conversion to the MKS system of units can be achieved by dividing the momentum in GeV/c by the speed of light.
Distance and time in natural units
– In particle physics, a system of natural units is widely used, where the speed of light and the reduced Planck constant are dimensionless and equal to unity.
– Distances and times are expressed in inverse energy units, while energy and mass are expressed in the same units.
– The conversion factors between electronvolt, second, and nanometer are provided by the values of the reduced Planck constant.
– Mean lifetime of an unstable particle can be expressed in seconds using its decay width in eV.
– Particle scattering lengths are often presented in units of inverse particle masses.
Temperature and energy
– In certain fields, such as plasma physics, the electronvolt is used to express temperature.
– The electronvolt is divided by the Boltzmann constant to convert to the Kelvin scale.
– The Boltzmann constant is approximately 1.380649×10^-23 J/K.
– The electronvolt to Kelvin conversion is about 11,604.518 K.
– A typical magnetic confinement fusion plasma is 15 keV, equivalent to 174 MK.
Wavelength and energy of photons
– The energy, frequency, and wavelength of a photon are related by the equation E = hc/λ.
– The Planck constant (h) and the speed of light (c) are used in the equation.
– The energy of a photon can be calculated as 4.135667516×10^-15 eV·s times the frequency (ν).
– The wavelength (λ) of a photon can be calculated as 1,239.84193 eV·nm divided by the energy (E) in eV. Source: https://en.wikipedia.org/wiki/Electronvolt
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacuum. When used as a unit of energy, the numerical value of 1 eV in joules (symbol J) is equivalent to the numerical value of the charge of an electron in coulombs (symbol C). Under the 2019 redefinition of the SI base units, this sets 1 eV equal to the exact value 1.602176634×10−19 J.
Historically, the electronvolt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences, because a particle with electric charge q gains an energy E = qV after passing through a voltage of V. Since q must be an integer multiple of the elementary charge e for any isolated particle, the gained energy in units of electronvolts conveniently equals that integer times the voltage.
