NEETPhysicsSemiconductors
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): A photodiode is preferably operated in forward bias condition for measuring light intensity. Reason (R): The fractional change in minority carrier current due to photo-excitation is more easily measurable than the fractional change in majority carrier current. In the light of the above statements,
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A).
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A).
- C(A) is true but (R) is false.
- D(A) is false but (R) is true.
Correct answer
D. (A) is false but (R) is true.
Step-by-step solution
A photodiode is preferably operated in reverse bias condition, not forward bias. Therefore, the Assertion is false. When a semiconductor is illuminated, the fractional change in minority carriers is much larger than the fractional change in majority carriers. Since reverse current is dominated by minority carriers, the change in reverse current due to photo-excitation is more easily measurable. Therefore, the Reason is true. Answer: (A) is false but (R) is true.