An isolated atom of a certain element emits light of wavelength λm1 when the atom falls from its state with quantum number m into its ground state of quantum number 1. The atom emits a photon of wavelength λn1 when the atom falls from its state with quantum number n into its ground state.
(a) Find the wavelength of the light radiated when the atom makes a transition from the m state to the n state.
(b) Show that kmn = |km1 - kn1|, where kij = 2π/λij is the wave number of the photon. This problem exemplifies the Ritz combination principle, an empirical rule formulated in 1908.