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14. Semicondutor electronics — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics14. Semicondutor electronics1 Mark
MCQ
An $LED$ (Light Emitting Diode) is constructed from a $p-n$ junction based on a certain $Ga-As-P$ semi-conducting material whose energy gap is $1.9\, eV$. What is the wavelength of the emitted light?
  • ✓
    $650\, nm$
  • B
    $65\,\mathop A\limits^o $
  • C
    $800\, nm$
  • D
    $8000\,\mathop A\limits^o $
✓

Answer

Correct option: A.
$650\, nm$
a
The wavelength of emitted light

$\lambda=\frac{h c}{E_{g}}$

where $\mathrm{E}_{\mathrm{g}}=$ energy gap of semiconductor

$=1.9\, \mathrm{eV}$

$=1.9 \times 1.6 \times 10^{-19} \,\mathrm{V}$

$\lambda=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{1.9 \times 1.6 \times 10^{-19}} \,\mathrm{m}$

$=6.5 \times 10^{-7}\, \mathrm{m}$

$=650 \times 10^{-9}\, \mathrm{m}$

$=650 \,\mathrm{nm}$

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