The wavelength of Lyman series is

$\frac{1}{\lambda}=R_H\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]$. For Lyman series $n_1=1$ and $n_2=2,3,4$, When $n_2=2$, we get $\lambda=\frac{4}{3 R_H}=\frac{4}{3 \times 10967}$ cm