(N/A) The velocity of an electron moving around a proton in a hydrogen atom in an orbit of radius $r = 5.3 \times 10^{-11} \, m$ is $v = 2.2 \times 10^{6} \, m/s$.
The frequency of the electron revolving around the proton is given by the formula $f = \frac{v}{2 \pi r}$.
Substituting the values:
$f = \frac{2.2 \times 10^{6} \, m/s}{2 \times 3.14 \times 5.3 \times 10^{-11} \, m}$
$f \approx 6.6 \times 10^{15} \, Hz$.
According to classical electromagnetic theory,the frequency of the electromagnetic waves emitted by a revolving electron is equal to the frequency of its revolution around the nucleus. Therefore,the initial frequency of the light emitted is $6.6 \times 10^{15} \, Hz$.