Generalized correspondence principle for the Bohr atom.---It is shown that when an electron spirals in from an orbit of quantum number
n2 to an orbit of quantum number
n1, the frequency of the radiation emitted is equal to an integer (${n}_{2}\ensuremath{-}{n}_{1}$) times the mean frequency of rotations in its orbit during the spiraling, assuming that the number of rotations made for a change of quantum level
dn is proportional to
dn. That is, the mean is defined as the ratio to (${n}_{2}\ensuremath{-}{n}_{1}$) of the integral from
n1 to
n2 of ${\ensuremath{\nu}}_{\mathrm{c}} \mathrm{dn}$ where ${\ensuremath{\nu}}_{c}$ is the classical frequency of rotation corresponding to any value of
n. No explanation is offered as to why radiation begins and stops at integral values of
n, nor why the radiation emitted in the manner assumed is monochromatic.