1. The eye
S8P4 b, c

2. Types of lenses
Convex- a lens that is curved outward, like the bottom of a spoon
Light rays will move away from each other if being reflected but towards each other if they are going through the lens.
Concave– a lens that is curved inward towards the center, like the inside of a spoon
Light rays will move towards each other if being reflected but away from each other if the waves are traveling through the lens
Where they meet is called the focal point

4. The eye gathers and focuses light
Eyes transmit light, refract light, and respond differently to wavelengths of different lights
Natural lenses
Eyes send signals to brain which interprets as shape, brightness, and color

5. How light travels through the eye

6. Vocabulary to know Cornea—a transparent membrane that covers the eye
Pupil—a circular opening that controls how much light enters the eye
Iris—surrounds the pupil and changes the size of the pupil
Lens—attached to small muscles that contract and relax to control the amount of refraction that occurs allowing the focal point to move so you can see near and far objects
Retina—an area in the back of the eye that contains specialized cells that responds to the light and sends signals through the optic nerve to the brain

7. How the eye forms images
Retina must focus on an image
Images are upside down but the brain interprets it as being right-side up
Retina also detects brightness and color
Rod cells—distinguish between white and black and shades of gray, helps with night vision
Cone cells—three types of cones (one each from red, blue, and green) that combine when needed

9. Corrective Lenses
Blurry images are caused when images from the lens does not fall exactly on the retina
Shape of eye
Lens not working properly
Artificial lenses are used to fix this problem

10. Corrective Lenses continued…
Nearsighted—cannot see objects far away
Focal point is in front of the retina
Corrected with concave lenses
Farsighted—cannot see object near to you
Focal point behind the retina
Corrected with convex lenses

11. Surgery
Cornea is responsible for 2/3 of the refracting so surgery can be done on the cornea to change the shape so it will move the focal point back to the retina
Nearsighted-remove tissue from the middle to make the cornea flatter
Farsighted-remove tissue from the outer edges to make the middle seem higher

12. Contact Lenses
Fit directly on the eye by floating on a thin layer of tears
Changes the way light is refracted in the eye