The potential of a P-N junction diode is 50 meV. When an electron having energy 400 meV travel from P to N after crossing the junction the energy of the electron is

Dear Student,
                       Potential has unit of  V or mV not MeV . MeV is unit of potential energy.
                      If  potential energy required to cross the junction is 50MeV then electron having
                      energy 400MeV after crossing the junction will have 350MeV .
Regard