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 |V_z| \gt \pm v \ge |v_0| where v_0 is the threshold voltage and V_z is the breakdown voltage. In the light of the above statements, choose the correct answer from the options given below

Both A and R are true but R is NOT the correct explanation of A

Both A and R are true and R is the correct explanation of A

Electronic Devices PYQ — JEE Main 2023 · 25 Jan · Shift 1 · Q50 with Solution

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Correct answer: D

Evaluate Assertion A

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

This is false.
- A photodiode is generally operated in reverse bias.
- In reverse bias, the reverse current is very small in darkness, but when light falls on the junction, electron-hole pairs are generated and the reverse photocurrent increases.
- This photocurrent is proportional to light intensity, so photodiodes are used in reverse bias for light detection.
Hence, Assertion A is false.
Evaluate Reason R

Reason R states that for a p-n junction diode, at applied voltage $V$ , the current in forward bias is more than the current in reverse bias for $|V_z| > \pm v \ge |v_0|$ where $v_0$ is threshold voltage and $V_z$ is breakdown voltage.

Interpreting the physical meaning:
- In forward bias, once the applied voltage exceeds the threshold voltage $v_0$ , the current rises rapidly.
- In reverse bias, current remains very small until the breakdown voltage $V_z$ is reached.
- Therefore, for voltages whose magnitude is above threshold but below breakdown, the forward current is much greater than reverse current.
So the Reason R is true.
Match with options
- Assertion A: False
- Reason R: True
Therefore, the correct option is: $\boxed{D}$
Comparison with stored answer

Stored correct answer: D

My derived answer also is D, so they agree.

View written solutionFree

Correct answer: D

Evaluate Assertion A

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

This is false.
- A photodiode is generally operated in reverse bias.
- In reverse bias, the reverse current is very small in darkness, but when light falls on the junction, electron-hole pairs are generated and the reverse photocurrent increases.
- This photocurrent is proportional to light intensity, so photodiodes are used in reverse bias for light detection.
Hence, Assertion A is false.
Evaluate Reason R

Reason R states that for a p-n junction diode, at applied voltage $V$ , the current in forward bias is more than the current in reverse bias for $|V_z| > \pm v \ge |v_0|$ where $v_0$ is threshold voltage and $V_z$ is breakdown voltage.

Interpreting the physical meaning:
- In forward bias, once the applied voltage exceeds the threshold voltage $v_0$ , the current rises rapidly.
- In reverse bias, current remains very small until the breakdown voltage $V_z$ is reached.
- Therefore, for voltages whose magnitude is above threshold but below breakdown, the forward current is much greater than reverse current.
So the Reason R is true.
Match with options
- Assertion A: False
- Reason R: True
Therefore, the correct option is: $\boxed{D}$
Comparison with stored answer

Stored correct answer: D

My derived answer also is D, so they agree.