$A$ $p-n$ photodiode is manufactured from a semiconductor with a band gap of $3.1 \,eV$. Which of the following wavelengths can be detected by it?

  • A
    $4000 \,\mathring{A}$
  • B
    $3900 \,\mathring{A}$
  • C
    $4200 \,\mathring{A}$
  • D
    Both $(a)$ and $(b)$

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