Question

Explain why quantum mechanics explain the turn-on voltage of differently colored LEDs. Use words, equations, and diagrams

Answer 1

The Quantum theory is based on atomic and subatomic particles like photons .

Photons are responsible for the working action of LED s .

The LED is a simple p-n junction diode specially doped when the light emits in forward direction it is called as Light Emitting Diode .  

The light emitting diode works like a normal diode. When the diode is forward biased the electrons and holes are moving fast across the junction and they are combining constantly.

When the electrons moves from the n-type to the p-type silicon they combines with the holes and disappears. Hence it makes the complete atom stable and it gives the little burst of energy in the form of a tiny packet called photon of light.

The different types of semiconductor materials are responsible for the different types of radiations and colour.

The flow of current in the semiconductors is caused by the both flow of holes in the opposite direction of current and flow of electrons in the direction of the current. Hence there will be recombination due to the flow of these charge carriers.

The recombination indicates that the electrons in the conduction band jump down to the valence band. When the electrons jump from one band to another band the electrons will emit the electromagnetic energy in the form of photons and the photon energy is equal to the forbidden energy gap.

As we know that

And that energy is from the current generated by semiconductor action of LED

And with every associated wavelength we have different colours and radiations associated with it .

So the quantum theory which is related to light action is the one which gives action of LED.