The structure that focuses light onto the retina is the

• A. Cornea
• B. Iris
• C. Lens
• D. Optic nerve

Answer: (C)

In the eye, focusing light onto the retina is achieved mainly by the lens through accommodation. Light first passes through the cornea, which provides most of the eye’s refractive power, but the cornea’s shape is fixed and can’t adjust for distance. The lens sits behind the iris and can change its curvature: when focusing on close objects, the ciliary muscles contract, the lens becomes rounder and increases its refractive power; when focusing on distant objects, the muscles relax and the lens flattens. This adjustment brings the image into sharp focus on the retina. The optic nerve then carries that visual information to the brain, while the iris controls the amount of light entering. So, the structure that focuses light onto the retina is the lens.