2.87 near and distant objects

2.87 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity.

Rays of light from distant objects are almost parallel when they enter the eye. They require less bending and the cornea can manage most of it without help from the lens. Muscles in the ciliary body relax and the lens is pulled into a thinner shape by the suspensory ligaments. This provides the correct focusing power.

Rays of light from near object are already diverging when they enter the eye. They need much more powerful refraction to bend them to a focus on the retina. Muscles in the ciliary body contract and the lens swells to a more rounded shape This makes it more powerful and the rays are bent more to achieve a focused image on the retina.