The I-V characteristics of an operating photodiode are drawn in

The correct answer is Option (3) → Third quadrant

A photodiode is operated in reverse bias. In reverse bias the small current is very sensitive to the light falling on the junction, because the photo-generated carriers change the minority-carrier current.

Both the voltage and the current are then negative (reverse voltage, reverse current), so the I-V curves for different intensities lie in the third quadrant.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Optoelectronic Junction Devices – “… A Photodiode is again a special purpose p-n junction diode fabricated with a transparent window to allow light to fall on the diode. It is operated under reverse bias.”

Optoelectronic Junction Devices – “… Hence, photodiodes are preferably used in the reverse bias condition for measuring light intensity.”