The minimum energy $h{v}_0$ required to eject electron from the surace of a metal is called

The minimum energy required to exhibit Photo electric effect is known as Work function.

                           $\mathrm{Work} \mathrm{function} , \mathrm{W}={\mathrm{h\nu }}_{\mathrm{o}}$

Where  ${\mathrm{\nu }}_{\mathrm{o}}=\mathrm{Thresh} \mathrm{hold} \mathrm{frequency}$