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13 Cards in this Set
- Front
- Back
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Iris (3) |
-coloured , -made of muscle, -controls amount of life getting in |
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Lens |
-focuses light on retina -clear,flexible bag of fluid surrounded by circular -ciliary muscles that change shape of lens -suspensory ligaments that attach the lens to the ciliary muscles |
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Cornea |
Refracts light |
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Pupil |
increases/decreases in size because of iris |
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Blind spot |
Part of the retina with no light sensitive receptors |
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Optic Nerve |
Carries impulses to brain via sensory neurones |
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Retina |
Has receptor cells sensitive to light |
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How does it work ? |
1.Eye focuses light on retina 2.Cornea & lens refract rays of light so they converge at focal point on retina 3.This stimulates light sensitive receptor cells in the retina 4.This causes nerve impulses to pass along sensory neurones to the brain 5.Brain interprets impulses this process is called perception |
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Eye defects |
-Colour blindness:missing specialised cells in the retina which means you cannot distinguish between green and red light rays. -Long/Short Sight : Eyeball or lens being wrong shape so light does not accurately focus on the retina -Age: As eye muscles get older they loose their ability to change shape |
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Distant |
Light rays almost parallel when reach eye so : 1. Ciliary muscles relax 2. Suspensory ligaments taut 3.Lens=long and thin 4. Light only refracted slightly |
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Near |
Light rays reflected by a near object diverge so : 1.Ciliary muscles contract 2.Suspensory ligament go slack 3.Lens=short and fat 4. Light is refracted |
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Long sight |
-Eyeball too short -Lens stays short and thin -Convex lenses which converge light from near objects to focus on the retina |
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Short sight |
-Eyeball too long -Weak suspensory ligaments which cannot pull the lens into a thin. flat shape. -Concave lenses which diverges light rays so they focus on the retina |
