Question

What is the total energy (E) of a 2.53 MeV electron?( When energy is used as an adjective, it refers to the kinetic energy of the particle, K= 2.53 MeV.)

Answer 1

The total energy E is a sum of the kinetic energy K and the rest energy E₀=mc². For the electron the rest energy E₀=0.51 MeV. So, E=K+E₀=3.04 MeV.