The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is
1
4
0.5
2
The wavelength of last line of Balmer series
1λB=Rc122-1∞2=Rc4
The wavelength of last line of Lyman series
1λB=Rc112-1∞2=Rc
∴ λBλL=41=4