Pupil Response to Light Intensity

Steps:

• Pupils constrict in bright light to limit light entry and dilate in dim conditions to allow more light.
• Sunglasses reduce light reaching the eyes, causing pupil dilation despite sunny conditions.
• Removing sunglasses exposes eyes to full sunlight, triggering rapid pupil constriction.
• Identify the time on the graph where pupil diameter suddenly decreases, indicating sunglass removal.

Why C is correct:

• At C, pupil diameter sharply decreases, matching the physiological reflex of constriction to sudden bright light exposure per the pupillary light reflex.

Why the others are wrong:

• A: Pupil diameter is stable or increasing, suggesting sunglasses still on or no change in light.
• B: Gradual change indicates adjustment, not abrupt removal.
• D: Diameter may be increasing or steady post-event, not the initial drop from removal.

Final answer: C