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COMEDK2021PhysicsSemiconductors

What is the minimum band-gap of the LED diode?

Options

  1. A1.5 eV
  2. B1.6 eV
  3. C1.8 eV
  4. D0.8 eV

Correct answer

C. 1.8 eV

Step-by-step solution

For an LED to emit visible light, the photon energy must correspond to the visible spectrum (400 nm to 700 nm). Minimum band-gap corresponds to maximum wavelength (700 nm, red light): E_ min = hc _ max = 1240 , eV·nm 700 , nm 1.77 , eV 1.8 , eV Correct option: (3)

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