$\text{ If }917\stackrel{\mathrm{o}}{\mathrm{A}}$ be the lowest wavelength of Lyman series than the lowest wavelength of Balmer series will be…………$\stackrel{\mathrm{o}}{\mathrm{A}}$

Lowest wavelength in Lyman series will be
$$\begin{gathered} \begin{array}{l}\frac{1}{{\mathrm{\lambda }}_{\mathrm{L}}}={\mathrm{RZ}}^2(\frac{1}{1^2}-\frac{1}{{\mathrm{\infty }}^2})......\left(\mathrm{i}\right)\\ \mathrm{and}\mathrm{in}\mathrm{Balmer}\mathrm{series}\\ \frac{1}{{\mathrm{\lambda }}_{\mathrm{B}}}={\mathrm{RZ}}^2(\frac{1}{2^2}-\frac{1}{{\mathrm{\infty }}^2})....\left(\mathrm{ii}\right)\\ \mathrm{on}\mathrm{dividing},\mathrm{equation}\left(\mathrm{i}\right)/\left(\mathrm{ii}\right) \\ \frac{{\mathrm{\lambda }}_{\mathrm{B}}}{{\mathrm{\lambda }}_{\mathrm{L}}}=4\Rightarrow {\mathrm{\lambda }}_{\mathrm{B}}=4\times 917\stackrel{0}{\mathrm{A}}=3668\stackrel{0}{\mathrm{A}}\end{array} \end{gathered}$$