Pg. 506 - 511. The Eyeball The Eyeball Iris: coloured part of the eye that opens and closes to let...
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Transcript of Pg. 506 - 511. The Eyeball The Eyeball Iris: coloured part of the eye that opens and closes to let...
12.3– The Human Eyepg. 506 - 511
The Eyeball
The Eye by Bill Nye
Iris: coloured part of the eye that opens and closes to let in more or less light. In the centre you find the pupil
Pupil: opening where light enters the eye Cornea: Transparent bulge on top of the
pupil
Eye Anatomy
Lens: Clear part behind the iris◦ NOTE: Both the cornea & lens focus light &
cause it to converge on the back of the eye. Retina: Inner lining of eye that is made of
light-sensitive cells, called rods and cones. These cells receive light rays, process them & send electric signals to the optic nerve
Eye Anatomy
Optic Nerve: The nerve at the back of the eye that is attached to the retina. It transmits the electrical impulses from the retina to the brain◦ Since there are no light sensitive cells here, it
creates a blind spot but each eye compensates for the other
Eye Anatomy
Light entering our eyes is refracted The lens acts like a converging lens that
produces a smaller, real, inverted image on the retina.
Electrical impulses travel through the optic nerve to the brain
Brain flips the inverted image so what we see is upright
Human Vision
Accommodation is the changing of shape of the lens by ciliary muscles to allow a sharp focused image to form on the retina
By changing the eye’s shape, the focal length changes, allowing us to focus on distant and nearby objects
Accommodation
Accommodation does not always work well. This results in an inability to focus on objects and thus producing blurred vision
Focusing Problems
Inability to focus light from nearby objects (can see distant objects)
Light is focused behind the retina Caused by a thin cornea; or an eyeball that
is too short
Hyperopia (far-sightedness)
Corrected using converging contact lenses or eye glasses to help refract the light
A modified form of the converging lens, called a positive meniscus is used because it is thinner & more visually appealing than a basic converging lens
Hyperopia (far-sightedness)
Form of far-sightedness caused by a loss of accommodation as a person ages
Eye loses its elasticity as we grow older Corrected using glasses with converging
lenses
Presbyopia
Inability of the eye to focus light from distant objects (can see nearby objects)
Light is focused in front of the retina A modified form of the diverging lens, called
a negative meniscus, is used
Myopia (near-sightedness)
blurred or distorted vision
caused by an incorrectly shaped cornea
corrective lenses or laser eye surgery can be used to correct astigmatism
Astigmatism
Read pg. 506 - 511 Do #5, 7, 8 on pg. 511 Study for your Physics Unit Test (Chapters 10, 11, 12)
Homework