Sol. $\quad \mathrm{E}=\phi+\mathrm{K}_{\max }$ $$ \begin{aligned} & \phi=\frac{\mathrm{hc}}{\lambda_0} \\ & \mathrm{~K}_{\max }=\mathrm{eV}_0 \\ & 8 \mathrm{e}=\frac{\mathrm{hc}}{\lambda}-\frac{\mathrm{hc}}{\lambda_0} \\ & 2 \mathrm{e}=\frac{\mathrm{hc}}{3 \lambda}-\frac{\mathrm{hc}}{\lambda_0} \end{aligned} $$ on solving (i) \& (ii) $$ \lambda_0=9 \lambda $$