What is the black-appearing center of the eye that changes size in response to light?

What is the black-appearing center of the eye that changes size in response to light?

• A. Pupil
• B. Retina
• C. Cornea
• D. Lens

Answer: (A)

The opening in the center of the iris is the pupil, and that’s what changes size in response to light. It appears black because the inside of the eye absorbs light rather than reflecting it. The pupil adjusts its diameter through the iris muscles: in bright light the sphincter pupillae contracts to make the pupil smaller, limiting light; in dim light the dilator pupillae relaxes and the pupil widens to let more light in. The retina is the light-detecting layer at the back of the eye, the cornea is the clear front surface that helps refract light, and the lens changes shape to focus images but doesn’t regulate light entry.

The opening in the center of the iris is the pupil, and that’s what changes size in response to light. It appears black because the inside of the eye absorbs light rather than reflecting it. The pupil adjusts its diameter through the iris muscles: in bright light the sphincter pupillae contracts to make the pupil smaller, limiting light; in dim light the dilator pupillae relaxes and the pupil widens to let more light in. The retina is the light-detecting layer at the back of the eye, the cornea is the clear front surface that helps refract light, and the lens changes shape to focus images but doesn’t regulate light entry.