Question 19

A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is $$1.42$$ eV. The wavelength of light emitted from the LED is :

For an LED, the wavelength of emitted light is related to the band gap by:

$$E = \frac{hc}{\lambda}$$

Rearranging for $$\lambda$$ gives:

$$\lambda = \frac{hc}{E} = \frac{1240 \text{ eV·nm}}{E \text{ (eV)}}$$

With $$E = 1.42$$ eV, we have

$$\lambda = \frac{1240}{1.42} \approx 873.2 \text{ nm} \approx 875 \text{ nm}$$

Therefore, the correct answer is Option 3: 875 nm.

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