Physics - Modern Physics Question with Solution | TestHub

The radius of the $n$-th orbit of a hydrogen atom is given by $r_n=r_1{n}^2$.

Given the radius of the innermost orbit ($n=1$) is $r_1=5.3\times 10^{-11}\text{ m}=0.53\mathring{A}$.

For the fourth allowed orbit, $n=4$.

$r_4=0.53\times (4{)}^2\mathring{A}$

$r_4=0.53\times 16\mathring{A}=8.48\mathring{A}$

Answer: $8.48\mathring{A}$