In a hydrogen atom, which of the following electronic transitions would  involve the maximum energy change

From diagram

$\begin{array}{l}{\mathrm{E}}_1=-13.6-(-3.4)=-10.2\mathrm{eV}\\ {\mathrm{E}}_2=-13.6-(-1.51)=-12.09\mathrm{eV}\\ {\mathrm{E}}_3=-1.51-(-0.85)=-0.66\mathrm{eV}\\ {\mathrm{E}}_4=-3.4-(-1.51)=-1.89\mathrm{eV}\end{array}$
${\mathrm{E}}_3$ is least i.e. frequency is lowest.