A certain material is kept at very low temperature. It is observed that when photons with energies between 0.22 eV and 0.72 eV strike the material, only photons of 0.33 eV and 0.61 eV are absorbed. Next the material is warmed up so that it starts to emit photons. When it has been warmed up enough that 0.61 eV photons begin to be emitted along with 0.33 eV photons, what additional photon energy is observed to be emitted by the material?
additional emitted photon energy = eV