Eyes Key Concept: When light from an object enters your eye, your eye sends a signal to your brain and you see the.

Key Concept:
When light from an object enters your eye,
your eye sends a signal to your brain and
you see the object.
Parts of the Eye:
1. Cornea:
• The outer most part of your eye.
• Protects your eye.
• Acts like a lens to focus light on
to your retina.
Parts of the Eye:
2. The pupil: The dark part of your
eye, where light enters
3. The iris: The colored part of your
eye. It is a muscle that controls the
size of your pupil. (Therefore how
much light is coming in)
Parts of the Eye:
4. The retina: A layer of light sensitive
cells at the back of your eye where the
light is focused. Composed of:
• Rods that respond well in low
light. Allows you to see in shades
of gray.
• Cones work best in bright light and
allow you to see color.
Parts of the Eye:
5. Optic nerve: A group of nerve cells
that send the light signals to the brain
6. The brain: turns the signals into an
7. Tapetum: A colorful reflective layer
on the back of some animals eyes
which allows them to see better at
Optical Illusion
Sometimes the brain distorts reality,
incorrectly interpreting the environmental
clues that surround an object. Optical
illusions demonstrate this phenomenon.
What do you see?
Which square is larger?
In each of the two illustrations above, one square is surrounded by four
rectangles larger than the center square in one drawing, smaller in the other.
The center square that is surrounded by smaller rectangles appears to be larger
than the center square surrounded by larger rectangles. In reality, the center
squares are the same size.
Which figures are tallest and smallest?
Eye Problems
When the eye ball is too short or too
long, the image does not form on the
This makes the image seem blurred.
Glasses or contacts can be used to
correct the problem
A nearsighted person can see nearby
objects but distant objects seem
Images focus too short of the retina.
Concave lenses can correct this
Nearsighted eyes see
far objects blurry
because the image
focuses to early
before the retina.
A concave lens
corrects this by
refocusing light from
the image to the
correct spot.
A farsighted sees distant objects, but
nearby objects seem blurred.
Images focus too far behind the retina.
Convex lenses can correct this
Farsighted people see
objects far away just fine,
but their eye incorrectly
focuses objects too far
past the retina.
Convex lenses correct
Farsightedness by
refocusing the light
correctly to the focal point
Blind Spot
On our retina there is a blind spot.
When objects get too close, we are
unable to see one spot of the object.
Try this by making a floating sausage
with your fingers.

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