From Einstein's photoelectric equation the maximum kinetic energy of photoelectrons emitted from metal surface is ${\mathrm{E}}_{\mathrm{K}}$ and $\mathrm{W}$ is work function, then

${\mathrm{E}}_{\mathrm{K}}=\mathrm{hv}-\mathrm{W}$

If ${\mathrm{v}}_0$ is threshold frequency, then

$\mathrm{W}={\mathrm{hv}}_0$

$\therefore {\mathrm{E}}_{\mathrm{K}}=\mathrm{hv}-{\mathrm{hv}}_0=\mathrm{h}\left(\mathrm{v}-{\mathrm{v}}_0\right)$

From the above equation, it is clear that maximum kinetic energy of electron will increase almost linearly with increase in the frequency of the incident light.