Question

i) A LED emits visible light when its
(A) junction is reverse biased
(B) depletion region widens
C holes nd electron recombine
D junction becomes hot
​

Answer 1

Answer:

Ajunction is reverse biased

Answer 2

Option C is the correct answer.

A LED radiates visible light when its holes and electrons recombine. Because of the recombining of electrons and holes, current progression occurs in the PN junction diode and therefore LED emits light.

• When an electron and a hole interact and recombine the energy is not transmitted into heat energy or thermal vibrations. Instead, the energy is substituted into an electron within the conduction band, which is then facilitated to an energy higher in the conduction band.
• The migration of holes from the p-side to the n-side is very instant, accordingly, the flow of electrons into the p-side is the major source of the current production. In other words, migrating electrons are inserted into the p-side to recombine with the holes to provide a voluntary emission of photons.

Hence, option C is the correct answer.