A light emitting diode produces light when
Correct answer: B. it is forward biased and electrons recombine with holes, releasing energy as photons
- A. it is reverse biased and breaks down
- B. it is forward biased and electrons recombine with holes, releasing energy as photons
- C. it is heated
- D. current passes through a filament inside it
Explanation
Each recombination across the junction releases an energy equal to the band gap of the semiconductor, and in materials such as gallium arsenide phosphide that energy falls in the visible range. The colour therefore depends on the band gap of the material rather than on any coating. Because no filament is heated, an LED wastes far less energy than an incandescent lamp.
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About PN Junction
A PN junction forms when p type and n type semiconductor regions meet, creating a depletion layer and a potential barrier. The topic covers forward and reverse bias, diode current voltage characteristics, breakdown and rectification, while distinguishing an ordinary junction diode from a transistor formed from multiple junctions.
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