\begin{aligned}
&\text { (c) फोटॉन की ऊर्जा, }\\
&\mathrm{E}=\frac{\mathrm{hc}}{\lambda}=3.03 \times 10^{-19}\\
&\text { or } \lambda=\frac{6.626 \times 10^{-34} \times 3 \times 10^{8}}{3.03 \times 10^{-19}}\\
&\text { or } \lambda=\frac{19.878}{3.03} \times 10^{-7}=6.56 \times 10^{-7}=656 \mathrm{nm}
\end{aligned}