Biology - Eye
- Created by: LunaShomeiRose
- Created on: 09-04-19 08:32
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- Eye
- Sensory organ with receptor cells (detect stimulus + sends impulse)
- Sensitive to light intensity + colour (stimulus)
- Structure
- Scurla - tough, supporting outer layer. Protects eye.
- cornea - transparent outer layer at front. Refracts (bends) light into eye
- Pupil - dark hole where light enters
- Iris - coloured part. Contains muscles to control pupil size (light)
- Lens - focuses light onto retina (fatter - focus short. Thinner - focus long)
- Ciliary muscle & suspensory ligament (smaller part) - control lens shape
- Retina - layer of receptor cells at back. Detect stimulus & convert to impulses)
- Optic nerve - carries impulses from retina to brain
- Too much light damages retina
- Musceles in iris control light intensity
- Dim - Radial muscles contract, dilates pupil, more light
- Bright - circular muscles contract, pupil constricts, less light
- Musceles in iris control light intensity
- Object sends light rays out in all directions.
- Light rays enter eye through cornea. As it does this, light refracts (converges)
- It focuses on Retina, forming flipped image of object
- Light rays enter eye through cornea. As it does this, light refracts (converges)
- Accommodation = changing lens shape to focus on objects
- Focusing on near object:Light diverging more so need thicker lens to converge back to a point
- Ciliary muscles contract. Sensory ligament loosens
- Focusing on far objects: rays less diverged so lens refracts less then for close object
- Cillar relax. Ligament contracts
- Focusing on near object:Light diverging more so need thicker lens to converge back to a point
- Eye problems: lens doesn't focus light on retina
- Myopia (short-sighted)
- Far objects blurred. Eye too long / cornea too curved. Refracts too strongly so rays focus in front of retina
- Concave (diverging lens).
- Diverages light before enter eye.
- Hyperopia (long-sighted)
- Near objects blurred. eye ball too short / cornea too flat. Image formed behind retina instead of on retina
- Convex (converging) lens
- Converge before enter eye, so able to focus on retina
- Eye contacts work same but are placed on eye
- Risk: eye infection
- Laser eye surgery. Reshapes cornea.
- Permanent - risk
- Replacement lens surgery. Lens placed permanently in eye
- Surgery - risk
- Myopia (short-sighted)
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