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 × 10 - 34 Js and c = 3 × 108 ms ⁻¹ ] (a) 654 nm and orange colour (b) 654 nm and red colour (c) 1046 nm and red colour (d) 1046 nm and blue colour

Answer: (b). λ = hc/Eg = 6.63×10⁻³⁴×3×10⁸1.9×1.6×10⁻¹⁹ m λ ≈ 6.54×10⁻⁷ m = 654 nm 654 nm lies in the red region ( 620 to 750 nm). So the answer is (b) 654 nm and red colour.

LED is constructed from Ga-As-P semiconducting material. The energy… | JEE Main 2021 (26 Feb, Shift 1)

Q62JEE Main 2021 · 26 FEB · SHIFT 1Easy

Special Purpose Diodes

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 ${}^{-1}$ ]

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Answer: (b)

$\lambda = \dfrac{hc}{E_g} = \dfrac{6.63\times10^{-34}\times3\times10^{8}}{1.9\times1.6\times10^{-19}}\ \text{m}$
$\lambda \approx 6.54\times10^{-7}\ \text{m} = 654\ \text{nm}$
$654$ nm lies in the red region ( $620$ to $750$ nm).
So the answer is (b) 654 nm and red colour.

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