Viva Questions:

Planck’s Constant determination by using light-emitting diodes (LEDs)

1. How is Planck’s constant determined? 
2. How it is different from Si/Ge diode?
3. How LED works?
4. In the photoelectric effect, a suitable frequency of photon falls on an electron in an atom and ejects the electron. In LED when electron-hole recombination takes place a photon emits. How do you see these two phenomena?

5. Why do you put equal two different energies like eV and hv, what is the condition for that?

6. Which material do we use an LED?

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7. How photons emitted from the LED and from which section of the LED?

8. How do you explain the working of LED by using the energy band diagram in forward biasing?

9. What happens when you provide the forward bias to the LED in terms of conduction band & valence band in the depletion region?

10. Why do not LED starts to glow immediately when you provide the forwarding bias to that?

11. Explain the concept of stopping potential in semiconductor diode V-I Characteristics?

12. Why does Blue color LED stopping potential is greater than the Red color LED?

13. Can we achieve the population inversion process in LED too? if yes what is the condition for that? if no then why?

14. What symbol do we use for the Light Emitting Diode?

15. What information do we get from the Planck’s Constant, and how one can say that radiation is in discrete form of energy?

Sources/Information Required to Explain/Understand the Experiment :

1. Working of a p-n Junction diode

2. Depletion region Concept/Idea along with potential barrier for Si/Ge

3. Semiconductor Material name that shows the optical property

4. Mainly energy band diagram of p-n junction diode and how electron transit from n to p side in depletion region in case of forward biasing.

5. The basic idea of electrical and radiation energy so can understand why they keep equal two different energy.