When light reflected from an object enters the eye, the following processes occur: • Light refraction: When light rays pass from one substance to another substance of different density, the rays bend, or refract. The amount of bending depends on the angle of incidence of the light ray and the degree to which the densities of the two substances differ. When distant objects are sighted, the normal curvature of the lens appropriately compensates for the refraction due to the differences in densities among the aqueous humor, the lens, and the vitreous humor. • Lens accommodation: Light rays from near objects enter the eyeball at more divergent angles than rays from distant objects. Thus, when near objects are sighted, muscles pull on the lens to increase its curvature so that the more divergent rays of the close object are properly refracted upon the retina. • Pupil constriction: One function of the pupil is to regulate the amount of light that enters the posterior cavity so that the retina receives the appropriate
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This note was uploaded on 11/10/2011 for the course PT 101 taught by Professor Staff during the Spring '10 term at Texas State.