What is the ratio of time periods `(T_(1)//T_(2))` in second orbit of hydrogen atom to third orbit of `He^(+)` ion?

Explanation

Time period `(T_(n)) = alpha (n^(2))/(Z^(2))`
`:. (T_(1))/(T_(2)) = (n_(1)^(3))/(Z_(1)^(2)) xx (Z_(2)^(2))/(n_(2)^(3)) = (2^(3))/(1^(2)) xx (2^(2))/(3^(3)) = (32)/(27)`