Question

In an atom, two electrons move round the nucleus in circular orbits of radii R and 4R. The ratio of the time taken by them to complete one revolution is : (Consider Bohr model to be valid)

• A. 1 : 4
• B. 4 : 1
• C. 1 : 8
• D. 8 : 1

Answer 1

Answer: (C)

1 : 8

Answer 2

$\frac{r_{1}}{r_{2}} = \frac{n_{1}^{2}}{n_{2}^{2}} = \frac{R}{4R} \Rightarrow \frac{n_{1}}{n_{2}} = \frac{1}{2} \therefore \frac{T_{1}}{T_{2}} = \frac{n_{1}^{3}}{n_{2}^{3}} = \frac{1}{8}.$