the eye Flashcards
Role of the Cornea
a transparent window that refracts incoming light to focus on the retina, helps the eye focus as light makes its way through
Role of the Pupil
the black hole in the iris that allows light to enter the eye.
Role of the Lens
refracts light to focus the image on the retina. Ciliary muscles thin out when focusing on distant objects, and thicken when focusing on near objects
Role of the Iris
The coloured part of the eye, changes size to control the amount of light entering the pupil (adjusts the size of the pupil)
Role of the Retina
Light-sensitive cells (rods and cones) change light energy into nerve impulses. Flips the image, the brain turns it back around
Role of the Optical Nerve
Takes messages from the retina to the brain
Role of the Sclera
a tough, protective, white outer layer that protects the eye
Role of Choroid
the black layer of blood vessels that provides nutrients
Role of Liquid Humour
helps keep the eyes shape, and provides the medium for the light to travel through. Watery at the front and jelly-like at the back
Role of Cones
Senses colour and requires more light than rods to work well. Sensitive to primary colours; red, blue and green, which together can sense combinations of light waves that let our eyes see millions of colours.
Role of Rods
A type of photoreceptor that sees in black and white, and shades of grey and tells us the form something has. Allows us to see when very dark
Myopia
- Nearsightedness
- Can see close up, not far away
- Caused by a too-long eyeball or a cornea that is curved steeply
- Diverging lens (concave) diverges light before it reaches the eye, then it is converged by the concave lens to produce an image on the retina
Hyperopia
- farsightedness
- can see distance, not up close
- caused by a too-short eye, or flat cornea
- Convex lens bends light rays towards one another before the concave lens bends it even more to create an image on the retina.
