The energy of a photon, whose momentum is 10 MeV/ c, where c is the speed of light, is- given by

The energy of a photon is directly related to its momentum through the relativistic energy-momentum equation. For a massless particle like a photon, the rest mass (m) is zero, simplifying the general relativistic formula E² = p²c² + m²c⁴ to E = pc. In this equation, E represents the total energy, p is the momentum, and c is the speed of light. Given that the momentum (p) is 10 MeV/c, we substitute this into the formula: E = (10 MeV/c) * c. The 'c' terms cancel out, resulting in an energy (E) of 10 MeV. This relationship is a fundamental principle in particle physics, where momentum is frequently expressed in units of MeV/c to simplify energy calculations. Therefore, a photon with a momentum of 10 MeV/c possesses an energy of exactly 10 MeV.

Sources

1. [1] http://www.hep.ph.ic.ac.uk/~dauncey/will/lecture02.pdf