Q12.28Long answer
The inverse square law in electrostatics is | F |= for the ( 4πε 0 ) .r 2 1 force between an electron and a proton. The dependence of r | F | can be understood in quantum theory as being due to the fact that the ‘particle’ of light (photon) is massless. If photons had a mass m p, force would be modified to e2 1 λ h | F |= 2 2 + .e ×p ( – λr ) where λ = m p c / and = . ( 0) πε r r r 2π Estimate the change in the ground state energy of a H-atom if m p were 10–6 times the mass of an electron.