b
\(\lambda1 = 10000\ Å, E = 1.23\ eV, \lambda_2 = 5000\ Å\)

\(, I = I_0,  I_S = 0.40 \times 10^{-6}\ Amp. No\ use\)

\({V_S} = \,\,1.36\,\,;\,\,\,\,\,\,\frac{{hc}}{{{\lambda _1}}} = 1.23\)

\(e{V_S} = \,\,hv - h{v_0}\,;\,\,\frac{{hc}}{{{\lambda _2}}} = \,\,{E_2}\)

\(hv_0 = hv - eV_S  ……(1)\) આપેલ છે.

\(hv = \frac{{{E_2}}}{{1.23}} = \frac{{{\lambda _1}}}{{{\lambda _2}}} = \frac{2}{1}\)

\( \Rightarrow \,{E_2} = 2 \times 1.23\, \Rightarrow \,hv = 2.46\)

\(eV \Rightarrow h{v_0} = 2.46\,\)

\( \Rightarrow \,h{v_0} = 2.46 - 1.36 = 1.1\,eV\)