A photon has an energy of 1.0 MeV. Calculate the frequency associated with this photon energy. State an appropriate unit in your answer.

The energy contained in a photon is given by the formula E = hf, where h is the Planck constant and f is the frequency of the photon. Since h = 4.110⁻¹⁵ eVs, f = E/h = 1.010³ eV / (4.110⁻¹⁵ eVs) = 2.110¹⁷s^-1. Note: if the Planck constant is provided in J*s is suffices to divide by the elementary charge to obtain the value used here.