Question

Draw a circuit diagram showing the biasing of an LED. State the factor which controls (i) wavelength of light, and (ii) intensity of light emitted by the diode.

Answer 1

Hint: As current passes through a light-emitting diode (LED), it produces light. Electrons recombine with electron holes in the semiconductor, producing energy in the form of photons. The energy needed for electrons to cross the semiconductor's band gap determines the colour of light (corresponding to the energy of photons). Multiple semiconductors or a sheet of light-emitting phosphor on the semiconductor device are used to provide white light.

Complete answer:

The forward bias condition is required for the Light Emitting Diode (LED) to work. The free electrons from the n-side and the holes from the p-side are forced into the junction while the Light Emitting Diode (LED) is forward biased. Any of the free electrons recombine with the holes in the positive ions as they meet the junction or depletion area.

Positive ions have fewer electrons than protons, as we remember. As a result, they're able to take electrons. In the depletion field, free electrons recombine with holes. In the depletion field, holes from the p-side recombine with electrons in a similar way.
(i) The band gap determines the energy and hence the wavelength of photons released.
(ii) As the intensity of light increases, the forward current increases and reaches a high.

Furthermore, an increase in forward current causes a reduction in brightness. The level of intensity LEDs are biased in such a way that their light-emitting efficiency is maximised.A wavelength of 743 nm leads to a band difference of 1.67 eV. There is a red light that is released.

Since no change of momentum is needed for an electron in the conduction band to recombine with a hole in the valence band, LEDs are often made of direct semiconductors.The external voltage is delivered over the P-N junction diode in forward bias or biasing. The P-side of the diode is connected to the positive terminal of the battery, while the N-side is connected to the negative terminal.

Note: High-power LEDs can be powered at currents ranging from hundreds of milliamperes to over an ampere, as opposed to tens of milliamperes for other LEDs. Some of them can produce over a thousand lumens. The system would malfunction in seconds if the heat from an HP-LED is not removed. In a torch, one HP-LED will sometimes replace an incandescent bulb, or an array of HP-LEDs can be used to create a powerful LED spotlight.