Q77 / 90 · JEE Main 2023 (25 Jan Shift 1) · Physics

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: Photodiodes are used in forward bias usually for measuring the light intensity.

Reason R: For a p-n junction diode, at applied voltage V the current in the forward bias is more than the current in the reverse bias for Vz>±V≥V0 where V0 is the threshold voltage and Vz is the breakdown voltage.

In the light of the above statements, choose the correct answer from the options given below

  • A
     Both A and R are true and R is correct explanation A 
  • B
    Both A and R are true but R is NOT the correct explanation A
  • Correct answer
    C
    A is false but R is true
  • D
    A is true but R is false 

Solution

Photodiodes are operated in reverse bias condition. The change in saturation reverse current in a photodiode with reverse bias is directly proportional to the change in light intensity, thus can be precisely measured.

Current in forward bias (for applied voltageV≥V0) is always greater than current in reverse bias (for V≤Vz ) in a p-n junction diode.

Hence, Assertion if false but Reason is true.

Hence, the correct answer is option: 'C'.

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