Question

A neutron breaks into a proton and an electron. Calculate the energy produced in this reaction is MeV. Mass of an electron $=9\times {10}^{-31}kg$, mass of proton $=1.6725\times {10}^{-27}kg$, mass of neutron $=1.6747\times {10}^{-27}kg$, and speed of light $=3\times {10}^{8}m{s}^{-1}$

Answer 1

Mass defect = mass of neutron $-$ (mass of proton + mass of electron)

or $\Delta m=1.6747\times {10}^{-27}-(1.6725\times {10}^{-27}+9\times {10}^{-31})=1.3\times {10}^{-30}kg$

Energy produced $=\Delta m\times c^2=1.3\times {10}^{-30}\times (3\times {10}^8{)}^2=1.16\times {10}^{-13}J=\frac{1.16\times {10}^{-13}}{1.6\times {10}^{-19}}=0.72MeV$ where $(1eV=1.6\times {10}^{-19}J)$