In Equation 26-26 we’ve given the value of the Rydberg energy in joules and in electron volts (eV). The energy that an electron acquires when it moves through a potential difference of 1 V is 1 eV, or approximately \(1.602 \times 10^{-19}\) J. To give you an idea of the amount of energy 1 eV represents, a photon of visible light carries between about 1.5 and 3 eV.