d
આપણને \(\,\lambda \,\, = \,\,\,2271\,\,\mathop A\limits^ \circ  \,\, = \,\,2271\,\, \times \,\,1{0^{ - 10}}\,m\,\,,\) \(\,{V_0} = \,\,1.3\,\,V\)  આપેલ છે.

\(hv\,\, = \,\,\,e\,{V_0}\, + \,\,{\phi _0}\)

\( \Rightarrow \,\,{\phi _0}\,\, = \,\,hv\,\, - \,\,e\,{V_0}\,\) અને

\(\,{\phi _0}\,\, = \,\,\frac{{hc}}{{{\lambda _0}}}\,\, - \,\,e\,\, \times \,\,1.3\,\,V\)

\( \Rightarrow \,\,{\phi _0}\,\, = \,\, \frac{{12400}}{{2271}} \,eV\,\, - \,\,1.3\,\,eV\,\, = \,\,5.5\,\,eV\, - \,\,\,1.3\,\,eV\,\, = \,\,4.2\,\,eV\)