In an experiment an atom in an excited state E3 sometimes decays directly to the ground state E0, emitting a single photon of energy 4.86eV. At other times it undergoes a two-step cascade E3→E1→E0, emitting photons of energies 3.01eV and 1.85eV, respectively. Assume E0 is defined as 0eV.
(1) Calculate the energy of the intermediate state E1 relative to the ground state.
(2) Demonstrate quantitatively that energy conservation holds for both the direct and cascade decays.