Verified Solution • 2025–26 Session moderate

QPages 419-421: Q9: HC Verma: Concepts of Physics - Volume 2 Semiconductors and Semiconductor Devices Pages 419-421: Q9 Solution: In a photo diode, the conductive increases when the material is …

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often multiply $h c$ by the wavelength instead of dividing, forgetting that photon energy $E=\frac{hc}{\lambda}$; use the inverse relationship and keep units consistent (eV·nm or convert $h$ and $c$ to SI before applying).

In a photo diode, the conductive increases when the material is exposed to light. It is found that the conductivity changes only if the wavelength is less than 620 nm. What is the band gap? Use Planck constant h=4.14×10−15 eV-sh = 4.14 \times 10^{-15} \text{ eV-s}, Boltzmann constant k=8.62×10−5 eV/Kk = 8.62 \times 10^{-5} \text{ eV/K}.)

Step-by-Step Verified Solution

**Answer:** Band gap = 2.0 eV. **Step-by-Step Explanation:** Given: Threshold wavelength = 620 nm.
E=1240620=2.0 eVE = \frac{1240}{620} = 2.0 \text{ eV}

All Questions in this Chapter

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