The eye S8P4 b, c

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

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

How light travels through the eye

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

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

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

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

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

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