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: $\large R(\frac{1}{1^2} – \frac{1}{2^2}) = R Z^2 (\frac{1}{2^2}-\frac{1}{4^2})$