If an electron is promoted from the third orbit of a hydrogen atom, they by how many times will the radius of the orbit be increased?

Explanation

The radius of the n-th orbit of H-atom, `r_(n)=(n^(2)h^(2))/(4pi^(2)me^(2))`
Radius of the first orbit `(r_(1))=(1^(2)xxh^(2))/(4pi^(2)me^(2))`
Radius of the third orbit `(r_(3))=(3^(2)xxh^(2))/(4pi^(2)me^(2))`
`therefore (r_(3))/(r_(1))=(3^(2)xxh^(2))/(4pi^(2)me^(2))xx(4pi^(2)me^(2))/(h^(2))=9` i.e., `r_(3)=9xxr_(1)`.
`therefore` The radius of the orbit will be increased by 9 times.