CUET · PHYSICS · PYQ PAPER 2023
The semiconductor used for fabrication of visible LEDs must at least have a band gap of :
- A \( 1.4 \text{ eV} \)
- B \( 1.8 \text{ eV} \)
- C \( 2.4 \text{ eV} \)
- D \( 3.0 \text{ eV} \)
Answer & Solution
Correct Answer
(B) \( 1.8 \text{ eV} \)
Step-by-step Solution
Detailed explanation
\( E_g \ge E_{\text{photon}} = \frac{hc}{\lambda} \) \( E_{\text{min,visible}} = \frac{1240 \text{ eV} \cdot \text{nm}}{700 \text{ nm}} \approx 1.77 \text{ eV} \) Thus, \( E_g \ge 1.77 \text{ eV} \). The smallest option satisfying this condition is \( 1.8 \text{ eV} \).
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