According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is

According to Einstein equation

$\mathrm{hv}={\mathrm{hv}}_{\mathrm{o}}+{\mathrm{K}}_{\max }\Rightarrow {\mathrm{K}}_{\max }=\mathrm{hv}-{\mathrm{hv}}_{\mathrm{o}}$

on comparing it with y = mx + c, it is clear to say that, 

This is the equation of straight line having positive slope (h) and negative intercept (${\mathrm{hv}}_{\mathrm{o}}$) on KE axis.