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Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsSemiconductor Electronic: Material, Devices And Simple Circuits1 Mark
Question
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from thecodes(a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion: Light Emitting Diode (LED) emit spontaneous radiation.
Reason: LED are forward-biased p-n junction.
✓

Answer

  1. Both A and R are true but R is not the correct explanation of A.

Explanation:

In semiconductor there may be energy bands due to donor impurities (ED) near the conduction band or acceptor impurities (EA) near the valence band. When electron falls from higher to lower energy level containing holes, the energy is released in the form of radiation. The energy of radiation emitted by LED is equal or less than the band gap of the semiconductor used. The radiation released lies in range of visible light whose colour depends on the semiconductor used.

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