Energy of incident radiation = Work function + Kinetic energy of photoelectron

Energy of incident raidation `(E)`

`=hv=h c/lambda`

`=((6.626xx10^(-34)J s)(3.0xx10^(8) m s^(-1)))/((256.7xx10^(-9)m))`

`=7.74xx10^(-19)J`

`=4.83 eV(1 eV=1.602xx10^(-19)J)`

The potential applied gives the kinetic energy to the electron.

Hence, kinetic energy of the elecyron`=0.35 eV`

:. Work function `4.83 eV-0.35 eV=4.48 eV`