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 For a hydrogen atom
it is given by
r
n
m
h
e
n = 





2
2
20
2
4
π
πε
The total energy is also quantised:
4
2
2
2
0
8
n
me
E
n
εh
= −
     = –13