Which statement about focusing on distant objects is true?

Which statement about focusing on distant objects is true?

• A. The lens becomes thicker
• B. The pupils dilate
• C. The ciliary muscles relax and the lens becomes flatter
• D. The iris controls pupil size

Answer: (C)

Focusing on distant objects relies on relaxation of the eye’s accommodation. When objects are far away, the incoming light is nearly parallel, so the eye doesn’t need extra refractive power. The ciliary muscles relax, which allows the zonular fibers to pull the lens into a flatter, thinner shape. A flatter lens has less curvature and therefore less optical power, enabling parallel rays to be focused on the retina. This is why the statement about the ciliary muscles relaxing and the lens becoming flatter is the correct description. The other ideas aren’t the primary mechanism for distance focusing: thickening the lens would increase focusing power for near tasks, pupil size changes are more about light levels and depth of field than distance accommodation, and while the iris does control pupil size, it isn’t the key driver of focusing on distant objects.

Focusing on distant objects relies on relaxation of the eye’s accommodation. When objects are far away, the incoming light is nearly parallel, so the eye doesn’t need extra refractive power. The ciliary muscles relax, which allows the zonular fibers to pull the lens into a flatter, thinner shape. A flatter lens has less curvature and therefore less optical power, enabling parallel rays to be focused on the retina.

This is why the statement about the ciliary muscles relaxing and the lens becoming flatter is the correct description. The other ideas aren’t the primary mechanism for distance focusing: thickening the lens would increase focusing power for near tasks, pupil size changes are more about light levels and depth of field than distance accommodation, and while the iris does control pupil size, it isn’t the key driver of focusing on distant objects.