AP Psychology Practice Test 2026 - Free AP Psychology Practice Questions and Study Guide

The lens is a transparent structure located behind the iris in the eye, and its primary function is to change shape in order to focus light rays onto the retina, which is crucial for clear vision. This process is known as accommodation. When you look at objects at different distances, the lens alters its curvature to ensure that light rays converge correctly on the retina, allowing you to see the object clearly, whether it is near or far.

Although the other options involve components of the visual system, they do not accurately describe the role of the lens. For instance, while the iris controls the amount of light entering the eye, this is not a function of the lens. Similarly, the lens does not control the pupil size, nor does it determine color hue, as those functions are linked to other structures in the eye and brain that process visual information. Therefore, focusing images through the change of shape is indeed the essential role of the lens in vision.