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

Explanation

The number of waves in any orbit `= ("circumference")/("wavelength") = (2pi r)/(lambda) = 2pi r xx (m v)/(h)`
The angular momentum of 3rd orbit is `(3h)/(2pi)`
Number of waves `= (2pi)/(h) xx (3h)/(2pi) = 3`