a
Energy \(E = \frac {hc}{\lambda };\) \(\frac{{{\lambda _N}}}{{{\lambda _A}}} = \frac{{{E_A}}}{{{E_N}}}\) where \(E_A\) and \(E_N\) are energies of photons from atom and nucleus respectively. \(E_N\) is of the order of \(MeV = 10^6\,\,eV\) and \(E_A\) in few \(eV.\) So \(\frac{{{\lambda _N}}}{{{\lambda _A}}}\, = \,{10^{ - 6}}\)