Chapter 5, Problem 45AP

Suppose an atom in an excited state can return to the ground state in two steps. It first falls to an intermediate state, emitting radiation of wavelength ${\lambda }_1$ , and then to the ground state, emitting radiation of wavelength ${\lambda }_2$ . The same atom can also return to the ground state in one step, with the emission of radiation of wavelength $\lambda$ . How are ${\lambda }_1,{\lambda }_2,$ and $\lambda$ related? How are the frequencies of the three radiations related?