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The Human Eye

The Human Eye. 13.6 Optics. Parts of the Human Eye. Optic Nerve Transmits electrical impulses from retina to brain. Creates blind spot at the back of each eye (but compensated for by other eye). Iris Coloured part of eye

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The Human Eye

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  1. The Human Eye 13.6 Optics

  2. Parts of the Human Eye Optic Nerve Transmits electrical impulses from retina to brain. Creates blind spot at the back of each eye (but compensated for by other eye) Iris • Coloured part of eye • Opens and closes around a central hole to control the amount of light that gets in Pupil The hole in the iris Cornea & Lens combination Cornea – transparent bulge over the lens Together, acts like a converging lens Produces a smaller, real, inverted image on the retina Retina Light sensitive cells in the retina convert light signals into electrical signals

  3. Parts of the Human Eye The brain • Takes inverted image from the retina and flips it so that the image we “see” appears upright

  4. Accommodation • ciliary (eye) muscles help the eye focus • slightly changes the shape of the eye lens

  5. Hyperopia (far-sightedness) Hyperopia (far-sightedness) Can see far / can not see nearby objects Cause: distance between lens and retina too small, or cornea-lens combination too weak Result:light from all nearby objects focuses behind the retina Solution: Far-sighted eyes need help refracting light a corrective converging lens (with a positive meniscus)

  6. Focusing Problems Presbyopia • A form of far-sightedness caused by a loss accommodation as a person ages • Eye lens just loses its elasticity

  7. Focusing Problems Myopia (near-sightedness) Can not see far / can see nearby objects Cause: Distance between lens and retina is too large, or cornea-lens combination converges light too strongly Result: light from distant objects is brought to focus in front of the retina Solution: a corrective diverging lens (with a negative meniscus)

  8. Focusing Problems Astigmatism • abnormal curvature of the cornea (oval shape) • can cause two focal points to fall in two different locations • objects up close and at a distance appear blurry

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