When it does so, a photon is emitted having energy equal
to the energy difference between the initial and final states The
frequency (n) of the emitted photon is then given by
hn  = Ei – Ef
An atom absorbs radiation of the same frequency the atom emits,
in which case the electron is transferred to an orbit with a higher
value of n Ei + hn  =  Ef
7 As a result of the quantisation condition of angular momentum, the
electron orbits the nucleus at only specific radii