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NEET 2009 (AIPMT) · Special Purpose Diodes

Special Purpose Diodes question from NEET 2009 (AIPMT)

Q94NEET 2009 · AIPMTEasy

Special Purpose Diodes

A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength

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Answer: (c)

  1. Detection needs hcλ≥Eg\dfrac{hc}{\lambda} \ge E_g, so λ≤12402.5 nm=496 nm\lambda \le \dfrac{1240}{2.5}\ \text{nm} = 496\ \text{nm}.
  2. Only 40004000 Å =400= 400 nm is shorter than 496496 nm.
  3. So the answer is (c) 40004000 Å.
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