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Eye- Sense Organ (Retina …
Eye- Sense Organ
Retina Contains the light Sensitive cells, Cones and Rods
Cones sense the Colour, Red Blue and Green
Packed mostly at the centre of the Retina. Objects are seen most clearly during daylight by looking at them directly.
Cones provide detailed images in colour. They only work in high light intensity
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The layer of pigment prevents internal reflection which might lead to multiple or blurred images. This is the black you see through the pupil.
Iris The coloured part of the eye which can expand and contract to control the amount of light entering the eye
Low Light Intensity: Radial muscle contract, circular relax. Pupil dilates. This allows more light to enter to increase visibility in low light areas.
High Light Intensity: Radial muscles relax, circular muscles contract. Pupil constricts. This prevents too much light from entering and prevents bleaching
Ciliary Muscle, Suspensory Ligament and Lens Together control light focusing on the retina.
Accomodation
Distant object. Light muscles need to be refracted less. Ciliary muscles relax and become spherical. Ligaments are tight. Lens is pulled long and thin
Close Object. Light must be greatly refracted. Ciliary muscles contract, pull eyeball inwards, bulges forwards. Ligaments relax. The lens becomes fat and short.
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Yellow Spot/ Fovea - It has high intensity of cones thus offers maximum sharpness but only works at full efficiency in bright light.
Optic Nerve Composed of Sensory Neurones which carry nerve impulses to the visual centre at the rear of the brain
Blind Spot Exit point of the Optic Nerve. No light sensitive cells here, light falling on this region cannot be detected.wk
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Pupil Circular opening which lets light into the eye. It appears black because the choroid is visible throughout it.