Hydrogen (\({}_1\mathrm{H}^1\)), Deuterium (\({}_1\mathrm{H}^2\)), singly ionised Helium (\(({}_2\mathrm{He}^4)^+\)) and doubly ionised lithium (\(({}_3\mathrm{Li}^6)^{++}\)) all have one electron around the nucleus. Consider an electron transition from \(n=2\) to \(n=1\). If the wave lengths of emitted radiation are \(\lambda_1,\ \lambda_2,\ \lambda_3\) and \(\lambda_4\) respectively then approximately which one of the following is correct ?