ABOUT THE EYE
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.
NEARSIGHTED EYE GLASSES
If the eye over converges and the light rays focus before they reach the retina, this is called nearsighted person. A nearsighted person can see nearby objects well, but for distant objects, it is hard for person to see clear. Therefore, to help nearsighted person to see clear they should wear glasses or contact lenses. The shape of lens help human eye changes the direction of the incoming light rays so the refractions in the eye have a clear image on the retina. So the shape of the lens is important because different kinds of lenses fix different kinds of problem.
Concave lenses are helping nearsighted people to correct their vision. They are thicker on the...