1. Convex and Concave LensesF
Convex and Concave Lenses F

2. Convex and Concave Lenses
A Concave lens is thinner and flatter in the middle, causing refracted light rays to diverge.
A Convex lens is thicker and rounder in the middle, causing refracted light rays to converge

3. The Human Eye & Sight

4. The Human Eye

5. Normal Vision The eye is remarkable! Light that is reflected
or emitted travels into
the eye through the
cornea. It passes
through the lens and
focuses on the retina at the back of the eye. Cells in the retina absorb this light and send the info along the optic nerve to the brain.

6. If your eye is functioning normally, the light image will converge at your retina, creating an inverted image.

7. The cillary muscles surrounding the lens contract and relax, therefore changing the shape of the lens.
cillary muscles
When the cillary muscles are relaxed distant objects are focused on the retina, when they are contracted, closer images are focused.

8. Nearsightedness (can see near)
The focal point of the light is to short to reach the retina. Light focuses in front of the retina.
A concave lens introduces divergence to correct focus.

9. Animation of Nearsightedness

10. Farsightedness The focal point of the light behind the retina
short to reach the retina. Light focuses in behind
A convex lens introduces convergence to correct focus.

11. Animation of Farsightedness