Question

In germanium, the energy gap is about $0.75eV$. The wavelength of light which germanium starts absorbing is

• A. $5000$$\stackrel{\circ }{A}$
• B. $1650$$\stackrel{\circ }{A}$
• C. $16500$$\stackrel{\circ }{A}$
• D. $165000$$\stackrel{\circ }{A}$

Answer 1

The correct option is C $16500$$\stackrel{\circ }{A}$

$E=\frac{hc}{\lambda }$
$\Rightarrow \lambda =\frac{hc}{E}=\frac{6.63\times {10}^{-34}\times 3\times {10}^8}{0.75\times 1.6\times {10}^{-19}}=16500\stackrel{\circ }{A}$