Calculate the wavelength emitted during the transition of an electron in between two level of `Li^(2+)` ion whose sum is `4` and difference is `2`.

Explanation

Suppose the transition takes place between levels `n_(1) and n_(2)`
Then `n_(1) + n_(2) = 4 and n_(2) - n_(1) = 2`
Solving these equations, we get `n_(1) = 1, n_(2) = 3 :. (1)/(lamda) = R ((1)/(n_(1)^(2)) - (1)/(n_(2)^(2))) Z^(2)`
For `Li^(2+) , Z = 3 :. (1)/(lamda) = 109, 677 cm^(-1) ((1)/(1^(2)) - (1)/(3^(2))) xx 3^(2) = 109, 677 xx ((1)/(1) - (1)/(9)) xx 9 cm^(-1) = 109677 xx 8 cm^(-1)`
or `lamda = (1)/(109677 xx 8 cm^(-1)) = 1.14 xx 10^(-6) cm`