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 ‚ 1019 J œ 6.56 ‚ 1019 J
so its frequency is
0 œ IÎ2 œ Ð6.56 ‚ 1019 JÑÎÐ6.63 ‚ 1034 J † sÑ
œ 9.9 ‚ 1014 Hz.