Question

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:

• A. 650 nm
• B. 1243 nm
• C. 875 nm
• D. 1400 nm

Answer 1

Answer: (C)

875 nm

Answer 2

The wavelength of light emitted from an LED is related to its energy gap by the formula:

$\lambda = \frac{1240}{E_g}$,

where:

• $\lambda$ is the wavelength in nanometers (nm),
• $E_g$ is the energy gap in electron volts (eV).

Substitute $E_g = 1.42 \, \text{eV}$:

$\lambda = \frac{1240}{1.42}$.

Perform the calculation: $\lambda = 875 \, \text{nm} \, \text{(approximately)}.$
Final Answer: 875 nm.