Question

Number of waves made by a Bohr electron in one complete revolution in 3^rd orbit is

• A. 2
• B. 3
• C. 4
• D. 1

Answer 1

Answer: (B)

3

Answer 2

Circumference of 3^rd orbit = $2\pi r_{3}$

According to Bohr angular momentum of electron in 3^rd orbit is

mvr₃ = $3\frac{h}{2\pi}$ or $\frac{h}{mv} = \frac{2\pi r_{3}}{3}$

by De-Broglie equation, $\lambda = \frac{h}{mv}$

$\therefore\lambda = \frac{2\pi r_{3}}{3}$ $\therefore 2\pi r_{3} = 3\lambda$

i.e. circumference of 3^rd orbit is three times the wavelength of electron or number of waves made by Bohr electron in one complete revolution in 3^rd orbit is three.