A p-n photodiode is fabricated from a semiconductor with a band gap of $2.5 \mathrm{eV}$. It can detect a…

A p-n photodiode is fabricated from a semiconductor with a band gap of $2.5 \mathrm{eV}$. It can detect a signal of wavelength :
  1. $4960 Å$
  2. $6000 Å$
  3. $4000 \mathrm{~nm}$
  4. $6000 \mathrm{~nm}$

Solution

$\begin{aligned} \lambda_{\max } & =\frac{\mathrm{hc}}{\mathrm{eV}} \\ & =\frac{1242 \mathrm{eV} Å}{2.5 \mathrm{eV}}=4960 Å \end{aligned}$

Asked in: NEET 2009 (Mains)

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