Final answer:
When a person with normal vision views an object close up, the lens thickens to focus the image on the retina.
Step-by-step explanation:
When a person with normal vision views an object close up, the lens thickens to focus the image on the retina.
The lens in the human eye has the ability to change its shape to adjust the focal length, a process called accommodation. This allows the eye to focus on objects at various distances. When looking at something up close, the ciliary muscles contract, causing the lens to become thicker. This increases the bending of light rays and brings the image into focus on the retina.