• # question_answer Ejection of the photoelectron from metal in the photoelectric effect experiment can be stopped by applying 0.5V when the radiation of 250nm is used. The work function of the metal is? [JEE Online 15-04-2018] A) $5.5\,\,eV$                 B) $4\,\,eV$        C) $5\,\,eV$                    D) $4.5\,\,eV$

From Ejection photoelectron $\because hv=h{{v}_{o}}+K.E.$ $\frac{hv}{x}=\phi +\text{Stopping}\,\,\text{pot}$ $\therefore \phi =\frac{hc}{x}-S.P.$ $=\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{250\times {{10}^{-9}}\times 1.6\times {{10}^{-19}}}-0.5\times 1.6\times {{10}^{-10}}$ $=\frac{6.6\times 3}{250\times 1.6}\times {{10}^{2}}-0.5$ $=4.95-0.5$ $\tilde{\ }4.5eV$