Q: The wavelength of the first line of Lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is
]
(a) 2
(b) 3
(c) 4
(d) 1
Ans: (a)
Sol: $\large R(\frac{1}{1^2} – \frac{1}{2^2}) = R Z^2 (\frac{1}{2^2}-\frac{1}{4^2})$