Verified Solution • 2025–26 Session moderate

QJEEM21Ph8070: JEE Main 2021 Physics - Class 12 JEEM21Ph8070 Solution: LED is constructed from Ga-As-P semiconducting material. The…

LED is constructed from Ga-As-P semiconducting material. The energy gap of this LED is 1.9 eV. Calculate the wavelength of light emitted and its colour.

[h = 6.63 ×\times 10 −- 34 Js and c = 3 ×\times 108 ms −- 1]

Multiple Choice Options

  • A 654 nm and orange colour
  • B 654 nm and red colour
  • C 1046 nm and red colour
  • D 1046 nm and blue colour

Step-by-Step Verified Solution

We know that E=hcλE = {{hc} \over \lambda }

λ=hcE⇒1240(in eV)E(in eV)\lambda = {{hc} \over E} \Rightarrow {{1240(in\,eV)} \over {E(in\,eV)}}

λ=12401.9\lambda = {{1240} \over {1.9}}

= 652.63 nm ≈\approx 654 nm

Wavelength of red light is 620 nm to 750 nm

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