Question

The number of waves in the fourth Bohr orbit of hydrogen is:

• A. 3
• B. 4
• C. 9
• D. 12

Answer 1

The correct option is B

4

Number of waves = $\frac{Circumference}{Wavelength}$

$\frac{2\pi r}{\lambda }$ = $\frac{2\pi r}{\frac{h}{mv}}$ = $\frac{2\pi }{h}\left(mvr\right)$ = $\frac{2\pi }{h}\times \frac{nh}{2\pi }=\frac{2\pi }{h}\times \frac{4h}{2\pi }$

$\therefore$ $n$ = $4$