What transition in the hydrogen spectrum would have the same wavelength as Balmer transitio, `n=4 " to "n=2` in the `He^(+)` spectrum?

Name the series of hydrogen spectrum which has least wavelength.

The first member of Balmer series in hydrogen spectrum has a wavelength of 6563overset@A .What will be the wavelength of Lyman series in the same spectrum ?

What is the wavelength in nm of the spectral line associated with a transition from n=3 to n= 2 for the Li^(2+) ion?

Name the part of the electromagnetic spectrum of wavelength 10^2 m