For emission line of atomic hydrogen from ${\mathrm{n}}_{\mathrm{i}}=8$ to ${\mathrm{n}}_{\mathrm{f}}=\mathrm{n},$ the plot of wave number $\left(\stackrel{-}{\mathrm{v}}\right)$ against $\left(\frac{1}{{\mathrm{n}}^2}\right)$ will be: (The Rydberg constant, ${\mathrm{R}}_{\mathrm{H}}$ is in wave number unit)

For any given series of spectral lines of atomic hydrogen, let  $\mathrm{\Delta }\stackrel{-}{\mathrm{v}}={\stackrel{-}{\mathrm{v}}}_{\mathrm{m}\mathrm{a}\mathrm{x}}-{\stackrel{-}{\mathrm{v}}}_{\mathrm{m}\mathrm{i}\mathrm{n}}$  be the difference in maximum and minimum wave number in $\mathrm{c}{\mathrm{m}}^{-1}$. 

The ratio $\mathrm{\Delta }{\stackrel{-}{\mathrm{v}}}_{\mathrm{L}\mathrm{y}\mathrm{m}\mathrm{a}\mathrm{n}}/\mathrm{\Delta }{\stackrel{-}{\mathrm{v}}}_{\mathrm{B}\mathrm{a}\mathrm{l}\mathrm{m}\mathrm{a}\mathrm{r}}$ is