Physics - Modern Physics Question with Solution | TestHub

Energy band gap range is given by, $${\mathrm{E}}_{\mathrm{g}}=\frac{\mathrm{hc}}{\lambda }$$ For visible region $$\begin{array}{rl}& \lambda =\left(4\times 10^{-7}\sim 7\times 10^{-7}\right)\mathrm{m}\\ & {\mathrm{E}}_{\mathrm{g}}=\frac{6.6\times 10^{-34}\times 3\times 10^8}{7\times 10^{-7}}\\ & =\frac{19.8\times 10^{-26}}{7\times 10^{-7}}\\ & =\frac{2.8\times 10^{-19}}{1.6\times 10^{-19}}\\ & {\mathrm{E}}_{\mathrm{g}}=1.75\mathrm{eV}\end{array}$$