OPTICS LAB (with Eye Dissection) Day
Name:__________________________
Hr/Date:________________________
1. What is our presenter’s name and what is his occupation?
____________________________________________________________________________
2.
How many times does the image invert as it is carried into our eye and to our brain? ______________
3. What else did he bring other than cow eyes and eye models/posters? __________________________
_____________________________________________________________________________
4.
Write the name of one of the optical illusions you looked at: _______________________________
5.
Was that optical illusion your favorite? _______ Why? ____________________________________
__________________________________________________________________________
6.
Name three of the diseases shown in the models on station 5 that were brought by Dr. Repsher:
__________________________________________________________________________________
Describe one of the three you listed: _____________________________________________________
__________________________________________________________________________________
7.
What was your vision from the vision test? Right eye _____________ Left Eye _____________
8. From the color blindness test, is there a concern for you about a possibility of color deficiency?
____________ If so, which one did you have difficulty with? _____________________________
9.
During the eye dissection section, what is the reflective part inside the cow eye that sits on top of the
Choroid and reflects light back out through the retina? Hint: our eyes do not have this part
______________________________________
10. Where were the cow eyes donated from? ________________________________________________
11. Were you able to touch part of the eye? ____________ If so, which part? _______________________
12. When you go to each of the following websites, found within the Optics Lab page on the class
website, look up the items in the questions and find the answers before you look at the other links:
a.) At the link titled virtual dissection, http://www.exploratorium.edu/learning_studio/cow_eye/ on
the eye diagram, where is the blind spot located?
_____________________________________________________________________
b.) At the link titled Eye games http://library.thinkquest.org/J002330/games.htm :
Was your Blind Spot the same for both the left and right eye? _____________
On the optical illusions, Illusion #1 says “The straight lines on the box appear __________”
13. Write down the names of 2 of our volunteers (other than Dr. Repsher) who came to help today:
___________________________________________________________________________________
14. Can you make an optical illusion pencil drawing? Share below:
From Virtual dissection site:
At the Exploratorium, we dissect cows’ eyes to show people how an eye works. This Web site shows
photos and videos of a dissection. If you try this at home, wash your hands after the dissection. Wear latex
gloves if you have cuts in your hands.
Here’s a cow’s eye from the meat company. The white part is the sclera, the outer covering of the
eyeball. The blue is the cornea, which starts out clear but becomes cloudy after death.
Without moving your head, look up. Look down. Look all around. Six muscles attached to your eyeball
move your eye so you can look in different directions. Cows have only four muscles that control their eyes.
They can look up, down, left, and right, but they can’t roll their eyes like you can.
If you reach up and feel around your eye, you’ll feel the bone of your skull. There’s fat surrounding your
eyeball to keep it from bumping up against the bone and getting bruised.
In the cow’s eye dissection, we cut away all the fat and muscle so that we can see the eyeball. A clear
tough surface called the cornea covers the front of your eye and protects your eye. If you make a cut in the
cornea, a clear fluid oozes out. That’s the aqueous humor, which is made of protein and water. The aqueous
humor helps give the eye its shape.
Now we are going to cut through the sclera and divide the eye in half, right around the middle. The
cornea will be on the front half of the eye. The cornea is made of many layers of tissue. Watch the video to
hear the crunch of a scalpel cutting through those layers.
Here is the back half of the eye. With the cornea and the iris out of the way, you can see the lens. It
looks gray in this photo, but it’s really clear. The clear goo around the lens is the vitreous humor. The eyeball
stays round because it’s filled with this clear goo.
Here’s what you see if you look through the lens. Everything on the other side looks upside down and
backward. You can use the lens to make an image, a picture of the world. That’s what the lens does in your eye.
It makes a picture of the world on your retina.
You see the world because light gets into your eyes. Your eye uses that light to make an image of the
world inside your eye—just as a camera uses light to make a photograph.
To understand how your eye makes an image of the world, you need to know a little bit about lenses.
Learn about lenses and experiment with a magnifying glass to discover how light makes an image of the world
here.
Once you know how lenses work, you can follow the path of light through your eye and find out how
your eye uses light to make an image. You can do that here.
Have you ever looked through a magnifying glass? The
clear glass (or plastic) in a magnifying glass is a lens, like
the lens that’s inside your
eye.
Using the lens of a
magnifying glass, you can
bend light to make an
image of the world. Look
at the photo on the left.
We used a magnifying
glass to produce an
inverted image of a candle.
The photo on the right
shows how.
You can try the same thing at home. For instructions on
how to make an image with a magnifying glass, click
here.
What’s Going On?
Suppose you use your magnifying glass to make
an image of a tree on a sunny day. You hold
your lens between the tree and a piece of paper.
You move the lens to just the right spot. Voilà!
There’s an image of the tree. That image is
made of light.
Sunlight bounces off the tree and spreads out in
all directions. Your lens gathers the light shining
out in all directions from each spot on that tree
and bends that light so it all comes back
together on a single spot on your piece of paper.
So light shining from a leaf at the top of the tree
ends up on one spot on your paper. Light
shining from a spot on the tree’s trunk ends up
in a different spot on your paper. All these spots
of light blend together in your eye to make an
image.
This works because the lens in your magnifying glass is
carefully shaped to bend light in a particular,
predictable way. The lens is shaped to bend light rays
so that they come together and then spread apart to
make an image.
The lens of your magnifying glass is probably fat in the
middle and thin at the edges. If you took the lens out of
the magnifying
glass, it would look
like this:
The surface of this
lens is curved. It’s
that curve that
makes light bend
when it shines
through your lens.
We took this picture to show you what happens
when several beams of light encounter a lens.
When nothing gets in its way, light travels in a nice
straight line. But when you put a chunk of clear glass
or plastic in the way, light may not keep traveling
straight. If light encounters a piece of glass or plastic at
an angle, the light bends. The bigger the angle, the
more the light bends. The light may bend again when it
moves from inside the glass or plastic into the air. If
the light meets the air at an angle, the light bends. The
bigger the angle, the bigger the bend.
The beams of light shine through the clear plastic of the
lens and encounter the curved surface where the
plastic of the lens meets the air. Beams of light that
meet this surface straight on keep on going straight.
But some beams of light meet the curved surface at an
angle. Those beams bend. This lens is curved on one
side and flat on the other. The lens in your eye is
curved on both sides, but it works in the same way.
© Exploratorium | The museum of science, art and human perception
How does light let you see these words?
Here’s how:
Suppose you’re looking out the window on a
sunny day and you see a tree. You see that tree
because light from the sun hit that tree. Some of
that light reflected from the tree—it bounced off
the tree like a ball bouncing off a wall.
Some of that reflected light hit you right in
the eye. That reflected light goes through the
clear cornea of your eye. As it goes through the
cornea, it bends a little.
The light shines through your pupil, the dark
hole in the middle of your eye.
The light shines through the lens of your eye.
The lens in your eye bends the light that has
reflected from that tree to make a perfect little
upside-down picture of the tree on the back of
your eyeball. (Find out more about lenses and
how bending light makes pictures.)
At the back of your eyeball, there’s a layer of
cells that are sensitive to light called the retina.
When the picture of the tree shines on the retina,
the light-sensitive cells send messages to your
brain.
Your brain takes the information from your
retina and puts it together to make an image of
the tree in your mind.
Weird, isn’t it? You think you see the tree—
but what you see is the light that bounced off the
tree and got into your eye. Or if you really want
to get picky, what you really see is the fixed-up
picture that your brain makes up from the mixed
signals it gets from your eye. Amazing!
You can experiment to find out more about how
your eye works
Here’s the back of the eye with the lens
and vitreous humor removed. It’s shaped
like a bowl. On the inside of the bowl is a
thin film with red blood vessels running
through it. The retina contains lightsensitive cells that detect light.
The layer of light-sensitive cells at
the back of the eye. The retina
detects images focused by the
cornea and the lens. The retina is
connected to the brain by the optic
nerve.
The retina is attached to the back of the
eye at just one spot. It’s called your blind
spot. Because there are no light-sensitive
cells at that spot, you can’t see anything
that lands in that place on the retina. At
the blind spot, all the nerves from the
retina join to form the optic nerve.
© Exploratorium | The museum of science, art and human perception
The layer of light-sensitive cells at the back of the eye. The retina detects images focused by the cornea and the lens. The retina is
connected to the brain by the optic nerve.
The place where the optic nerve leaves the retina. Each eye has a blind spot where there are no light-sensitive cells.
The bundle of nerve fibers that carry information from the retina to the brain.
Here’s the inside of the back of the eye
again. Behind the retina is a layer of
shiny, blue-green stuff called the tapetum.
This layer assists night vision by reflecting
light back through the retina. You don’t
have a tapetum, but cats and cows (and
other animals) do. A cat’s eyes shine in
the headlights of a car because of the
tapetum.
© Exploratorium | The museum of science, art and human perception
The colorful, shiny material
located behind the retina. Found
in animals with good night vision,
the tapetum reflects light back
through the retina.
The layer of light-sensitive cells
at the back of the eye. The retina
detects images focused by the
cornea and the lens. The retina is
connected to the brain by the
optic nerve.
FROM EYE GAMES Website:
Stereograms
Stereograms are pictures that look like random patterns until your eyes focus on them in
a particular way, allowing you to see an image. If you can focus your eyes so that your
right and left eye are looking at separate parts of the image, your brain is tricked into
putting it together and forming a 3-D picture.
To see the hidden pictures, bring your eyes close to the screen, then slowly pull your
head away. Pretend that you're looking at something behind the image. You can also try
crossing your eyes, but the pictures will appear backwards and are much more difficult
to see that way.
#1 - bird landing
Blind Spot Test
Close your left eye, and with your right eye focus on the +. Keep your eyes about two
feet from your computer screen, then slowly bring your face closer to the screen.
When you get a certain distance away, the 0 should disappear. This is your blind spot.
Now, try it with your right eye closed, and focus your left eye on the 0.
Not everyone's blind spot is in the exact same place. In fact, for most people, the blind
spot varies between the left and right eye.
OPTICAL ILLUSIONS
These are a few optical illusions for you to have fun with.
An optical illusion is just a picture where the brain has trouble interpreting what the eye
sees.
Illusion #1
The straight lines on the box appear to be bent.
Illusion #2
Which side of the box is in front? We'll leave that up to you.
Illusion #3
How many legs does this elephant have?
Illusion #4
These long lines are actually
parallel, though they don't look it.
Illusion #5
Is this person a liar?
Illusion #6
Which line is shorter? Neither!
Illusion #7
Is this lady young or old?