PHGY 1030 Lecture Notes - Lecture 12: Brainstem, Pupillary Light Reflex, Retina
26 Jan 2013
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Document Summary
Cornea, rather than the lens, is the site of most of the refractive power of the eyes. Light strikes the cornea and passes from the air into the aqueous humor. Then light rays bend and converge on the back of the eye (see fig. Focal distance: the distance from the refractive surface to the point where parallel light rays converge and depends on the curvature of the cornea (i. e. tight the curve, the shorter the focal distance). Diopter: reciprocal of the focal distance in meters. The cornea has a refractive power of 42 diopters which means that parallel light rays striking the corneal surface will be focused 0. 024 m (2. 4 cm). Refractive power depends on the slowing of light at the air-cornea interface. If we replace air with a medium that passes light at about the same speed as the eye, the refractive power will eliminated. This is why one"s vision is blurry when you open your eyes underwater.
