Q137 / 197 · NEET 2009 (Mains) · Physics
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 :
- Correct answerA$496 Å$
- B$6000 Å$
- C$4000 \mathrm{~nm}$
- D$6000 \mathrm{~nm}$
Solution
$$
\text { } \begin{aligned}
\lambda_{\max } & =\frac{\mathrm{hc}}{\mathrm{eV}} \\
& =\frac{1242 \mathrm{eV} Å}{2.5 \mathrm{eV}}=4960 Å
\end{aligned}
$$
Hence, the correct answer is option: 'A'.