Question

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. $3$
• B. $4$
• C. $1$
• D. $2$

Answer 1

The correct option is D $2$

Given,

${\lambda }_B={\lambda }_L$

$R\times \frac{3}{4}=R\times \frac{3}{16}{Z}^2$

$Z^2=4$

$\therefore Z=2$