Question

The ratio of time taken by electron in revolutions round the H-nucleus in 2nd and 3rd orbits, are:

• A. $2:3$
• B. $4:8$
• C. $8:27$
• D. $27:8$

Answer 1

The correct option is C $8:27$

time taken for revolution $\propto \frac{r_n}{v_n}$

$t\propto \frac{n_2}{v_n}$

$t\propto n^3$

$\frac{\text{time taken revolution around}{2}^{nd}\text{orbit}}{\text{time taken in revolution in}{3}^{rd}\text{orbit}}$

$=\frac{2^3}{3^3}$

$=8:27$ option C is correct.