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 ______.

Options

• 650 nm

• 1243 nm

• 875 nm

• 1400 nm

Answer 1

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 875 nm.

Explanation:

Given: E_g = 1.42 eV

Planck’s constant (h) = 6.63 × 10⁻³⁴ J s

Speed of light (c) = 3 × 10⁸ m/s

When an electron falls across the band gap in an LED, it releases a photon. The energy of this photon is approximately equal to the band gap energy (E_g).

E_g = `(hc)/lambda`

λ = `(hc)/E_g`

= `((6.63 xx 10^-34) xx (3 xx 10^8))/1.42`

= `1242/1.42`

= 874.64 nm

≈ 875 nm

∴ The wavelength of light emitted from the GaAs LED is 875 nm, which falls in the infrared region of the spectrum.