The wavelength of first Lyman lines of Hydrogen (H), He+ and Li2+ ions are λ1, λ2 and λ3 respectively. The ratio λ1:λ2:λ3 is ______
(3)
1λ∝RnZ2 ⇒ λ1:λ2:λ3=112:122:132=1:14:19=36:9:4