An exact energy level is required to bring an electron from one orbital to another. For example with hydrogen, for an electron to go from the ground state to the third orbital requires a photon with an energy of 12.09eV. But what is the tolerance? In other words, how close to that frequency does the photon need to be, within 1%, .001%, or what? Also, is it ever possible for a photon with a slightly different frequency to be absorbed? Can a photon of 12.15eV cause the electron to jump to the third orbital and either … scatter the remaining energy as a 0.06eV photon? or absorb the excess energy as heat?