How do the lenses in eyeglasses help nearsighted and farsighted people see bette!
Question: i have to explain this to my mom who is getting glasses
Answers: i have to explain this to my mom who is getting glasses
I'm trying not to get too complicated; no point in overwhelming her with too much information.
In nearsighted people, typically the eyeball is a little too long, (front to back) so, when looking at distant objects, the eye's lens causes the image to focus a little in front of the retna and thus is see as out of focus. Since we can't easily change the shape of the eyeball, we treat the problem by the use of a concave lens, which partially counteracts the focusing effect of the convex lens in the eye (essentialy makes it as if the power of the lens in the eye was weaker). If the strength of the concave lens is properly chosen, the image again focuses at the retna and the person sees distant objects in focus again.
With farsighted people, the eyeball is a little too short, (front to back) so when looking at close objects, the focal point of the image is actually behind the retna so it will be seen as out of focus. A convex lens is used to make it as if the lens of the eye were a little stronger, so the image focuses in a shorter distance (to match the distance of the retna).
Hope this helps. there are probably web sites that describe this in better detail, if she is really interested. Also, at the eyeglass place, they might have some pamphlets about how glasses work, with diagrams etc.
Nearsighted and farsighted people can't see well because of the shape of their cornea, it is either shaped to flate or too narrow, Eyeglasses are made to level out the angle you are seeing from, Di'ya get it?
just to put it kinda simply the lens changes the way the light is reflected onto the cornea. (the bit behind ur pupil.)