Electronvolt (unit)

An electronvolt (eV) is defined as the energy required to accelerate a single electron at rest through an electron potential difference of 1 volt in a vacuum.

1 eV ≈ 1.603 x 10 J

Electronvolts are a more mathematically convenient method to describe the miniscule quantity of energy associated with photons in imaging physics.

The energy required in diagnostic x-rays fall within the range of kiloelectronvolts (keV), whereas the energy required in radiotherapy is often in terms of megaelectronvolts (MeV).