Human eyes receive and form images from outside, also automatically changes in light and seeing things close up and at a distance. Therefore, we can see most of things from outside world. But without light, we can't see anything. Light travels though space and the sun gives off light rays then enter the eyes they are bent or refracted and these light rays create images or picture of all the objects around you, that's why we can see things very clearly. How light enter the eye, first light enters the eye though pupil which control different amounts of light into our eye. Then crystalline lens helps us see clearly, when we look at near objects crystalline lens will grows thicker and when we look at far objects then it will grows flatter. The crystalline lens and the cornea (the window of the eye) are bending light rays and sending them to the retinain the right direction. For our perfect vision, light rays must focus at one point on the retina.
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The lens of the eye can change its shape to rounder when you see a close object, because this shape can bends light rays more sharply then they converge to a focus on the retina |