OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What typically happens to a pupil in response to bright light?

1. It expands

2. It contracts

3. It remains unchanged

4. It turns red

The correct answer is: It contracts

In response to bright light, the pupil of the eye contracts. This reaction is part of the eye's reflex control, specifically known as the pupillary light reflex. When bright light hits the retina, specialized cells in the retina send signals to the brain, which then signals the muscles of the iris to constrict the pupil. This contraction reduces the amount of light entering the eye, which helps to protect the retina from damage caused by excessive brightness and also improves the clarity of vision by increasing the depth of focus. In darker situations, the opposite occurs—the pupil dilates to allow more light to enter the eye, enhancing vision under low-light conditions. The ability of the pupil to adjust in size according to light intensity is a critical function for optimal vision and protects the sensitive tissues in the eye.