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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

The Human Eye

13.6 Optics

Parts of the human eye
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)


  • Coloured part of eye

  • Opens and closes around a central hole to control the amount of light that gets in


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


Light sensitive cells in the retina convert light signals into electrical signals

Parts of the human eye1
Parts of the Human Eye

The brain

  • Takes inverted image from the retina and flips it so that the image we “see” appears upright


  • ciliary (eye) muscles help the eye focus

  • slightly changes the shape of the eye lens

Hyperopia far sightedness
Hyperopia (far-sightedness)

Hyperopia (far-sightedness)

Can see far / can not see nearby objects


distance between lens and retina too small, or cornea-lens combination too weak

Result:light from all nearby objects focuses behind the retina


Far-sighted eyes need help refracting light a corrective converging lens (with a positive meniscus)

Focusing problems
Focusing Problems


  • A form of far-sightedness caused by a loss accommodation as a person ages

  • Eye lens just loses its elasticity

Focusing problems1
Focusing Problems

Myopia (near-sightedness)

Can not see far / can see nearby objects


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


a corrective diverging lens (with a negative meniscus)

Focusing problems2
Focusing Problems


  • 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