The wavelength of spectral line for electron transition is inversely related to

$∆\mathrm{E}$ is the difference of energy in the energy levels. 

$∆\mathrm{E}={\mathrm{E}}_2-{\mathrm{E}}_1$

Also relation with $∆\mathrm{E}$ and wavelength.

$∆\mathrm{E}=\frac{\mathrm{hc}}{\mathrm{\lambda }}$

This indicates that wavelength is inversely proportional to the difference in energy between the energy level in the transition.