According to Einstein's photoelectric equation, the graph of KE of the photoelectron emitted from the
metal versus the frequency of the incident radiation gives a straight line graph, whose slope

According to Einstein's photoelectric equation,

${\mathrm{KE}}_{\max }=h\nu -{\varphi }_0$

           = h$\nu -h{\nu }_0$

Comparing with the equation of straight line

$y=m x+c$

We get, slope of graph between KE and v = h (i.e. same for all metals)

Experimentally

KE_max=h$\nu$-h${\nu }_0$

e V₀= h($\nu -{\nu }_0)$

V₀  =$\frac{h(\nu -{\nu }_0)}{e}$

$\frac{h}{e} is the slope$