CLASS EXERCISE #24 - 1 August 2005 An atom undergoes a transition from a state of energy 14.7 eV to a state of energy 10.6 eV. Determine whether a photon was absorbed or emitted, and determine that photon's energy (in both eV and joules) and frequency. The change in energy of the atom is ?I œ If Ii œ Ð10.6 eVÑ Ð Ð14.7 eVÑÑ œ 4.1 eV. Since this is positive, a photon must have been absorbed. The energy of this photon is I œ 4.1 eV œ 4.1 ‚ 1.6 ‚ 1019 J œ 6.56 ‚ 1019 J so its frequency is 0 œ IÎ2 œ Ð6.56 ‚ 1019 JÑÎÐ6.63 ‚ 1034 J † sÑ œ 9.9 ‚ 1014 Hz.