Q.Light emitting diodes emit light in which bias? OR Write the Boolean expression for NOR gate.

An LED is a forward-biased p-n junction diode; light is emitted only when the junction is forward biased, allowing electron-hole recombination that releases energy as photons.

A light emitting diode (LED) is a heavily doped p-n junction that emits light through spontaneous emission when charge carriers recombine. This recombination only happens efficiently when the diode is forward biased — the p-side connected to the positive terminal and n-side to the negative terminal of the source. Forward bias injects majority carriers (el …

An LED's emission colour (wavelength) is set by the semiconductor's band gap, while its brightness (intensity) is controlled by the forward-bias current.

An LED is a forward-biased p-n junction made of a direct band-gap semiconductor. When forward biased, electrons and holes are injected across the junction and recombine, releasing energy as photons.

• Wavelength: the photon energy released on recombination $\approx$ the band gap energy $E_g$, so $\lambda = hc/E_g$ — set by the material's energy gap. …

Among the given semiconductor compounds, GaInN (Indium Gallium Nitride) is the material used in white-light-emitting LEDs.

Working

Different LED materials emit different colours depending on their band gap:

• GaInN (Gallium Indium Nitride): emits blue/UV light efficiently and, combined with a yellow phosphor coating (or by combining red/green/blue chips), is the standard material used to produce white-light LEDs. …