An LED is constructed from a p-n junction diode using GaAsP. The energy gap is 1.9 eV. The wavelength of the light emitted will be equal to (a) 654 × 10⁻¹¹ m (b) 10.4 × 10⁻²⁶ m (c) 654 nm (d) 654 Å

Answer: (c). λ = hc/Eg λ = 6.63×10⁻³⁴×3×10⁸1.9×1.6×10⁻¹⁹ = 1.989×10⁻²⁵3.04×10⁻¹⁹ m λ ≈ 6.54×10⁻⁷ m = 654 nm So the answer is (c) 654 nm.

An LED is constructed from a p-n junction diode using GaAsP. The… | NEET 2019

Q79NEET 2019Easy

Special Purpose Diodes

An LED is constructed from a p-n junction diode using GaAsP. The energy gap is $1.9\text{ eV}$ . The wavelength of the light emitted will be equal to

Show answer and solution

Answer: (c)

$\lambda = \dfrac{hc}{E_g}$
$\lambda = \dfrac{6.63\times10^{-34}\times3\times10^{8}}{1.9\times1.6\times10^{-19}} = \dfrac{1.989\times10^{-25}}{3.04\times10^{-19}}\ \text{m}$
$\lambda \approx 6.54\times10^{-7}\ \text{m} = 654\ \text{nm}$
So the answer is (c) $654$ nm.