The pupil's size is controlled by the iris. In bright light, the iris muscles contract, causing the pupil to become smaller (constrict). In dim light, the iris muscles relax, causing the pupil to become larger (dilate). This mechanism is an involuntary reflex that protects the retina from overexposure to light and allows for adequate light to enter for vision in low-light conditions.
A person gets out in the sunlight from a dark room. How does his pupil regulate and control the light entering the eye?
Asked in ASO 2025 · Topic: Optics (Optical Instruments: microscopes, telescopes, human eye)
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Answer: B. The size of the pupil will decrease and less light will enter the eye
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