Energy required to stop the election of electrons from Cu plate is 2.24eV. If radiation of  $\lambda =253.7nm$ strikes the plate, the work function is

Energy of photon $\left(E_{Photon}\right)$

= work function + kinetic energy absorbed = $W_0+e{V}_0$

Where, e = electric charge

$V_0$ = stopping potential and e$V_0$= KE, i. e. energy required to stop the ejection of electrons.

$E_{Photon}=\frac{hc}{\lambda }$

$=\frac{6.626\times {10}^{-34}\times 3.0\times {10}^8}{253.7\times {10}^{-9}}$

$=7.835\times {10}^{-19}J$

$=\frac{7.835\times {10}^{-19}}{1.602\times {10}^{-19}}eV$

$\because E_{Photon}=W_0+0.24eV$

$\therefore W_0=4.65eV$