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 $$|V_z| > \pm V \geq |V_0|$$ 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

We need to evaluate the Assertion-Reason statement about photodiodes.

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

Analysis of A: This is FALSE. Photodiodes are used in reverse bias (or zero bias/photovoltaic mode) for measuring light intensity. In reverse bias, the photocurrent is proportional to the light intensity, and the dark current is minimal, making it ideal for light detection.

Reason R: For a $$p$$-$$n$$ junction diode, at applied voltage $$V$$, the current in forward bias is more than the current in reverse bias for $$|V_z| > \pm V \geq |V_0|$$, where $$V_0$$ is the threshold voltage and $$V_z$$ is the breakdown voltage.

Analysis of R: This is TRUE. For a p-n junction diode, in the voltage range between the threshold voltage and the breakdown voltage, the forward bias current is indeed greater than the reverse bias current. In reverse bias, only a small saturation current flows (until breakdown), whereas in forward bias beyond $$V_0$$, current increases exponentially.

Conclusion: Assertion A is false, but Reason R is true.

The correct answer is Option C: A is false but R is true.