The ratio of the wavelengths for `2 rarr 1` transition in `Li^(++), He^(+)` and `H` is

The ratio of the wavelength for the transition from n = 2 to n = 1 in Li^(++).He^(+) and H is

Which transition in Li^(2 +) would have the same wavelength as the 2 rarr 4 transition in He^(+) ion ?

Which transition in Li^(2 +) would have the same wavelength as the 2 rarr 4 transition in He^(+) ion ?

The wavelength correspoding to electronic transition between to orbit of hydrogen atom is 912 Å. The wavelength (in Å) for the same electronic transition in Li^(2+) is