Question

Find the number of waves made by a Bohr electron in one complete revolution in the $3^{rd}$ orbit.

Answer 1

Velocity of the electron in $3^{rd}orbit=\frac{3h}{2\pi mr}$
where, $m=$ mass of electron and $r=$ radius of $3^{rd}$ orbit.
Applying de Broglie equation,
$\lambda =\frac{h}{mv}=\frac{h}{m}\times \frac{2\pi mr}{3h}=\frac{2\pi r}{3}$
$\text{Number of waves}=\frac{2\pi r}{\lambda }=\frac{2\pi r}{2\pi r}\times 3=3$