In this lab, we are going to make an eyeball model using a balloon. This experiment should give you a better idea of how your eyes work. The way your brain actually sees things is still a mystery, but using the balloon we can get a good working model of how light gets to your brain.


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Here’s what you need


    • 1 biconvex plastic lens
    • 1 round balloon, white, 9 inches
    • 1 assistant
    • 1 votive candle
    • 1 black marker
    • 1 book of matches
    • 1 metric ruler
    • Adult Supervision!


Download Student Worksheet & Exercises


Here’s what you do


  1. Blow up the balloon until it is about the size of a grapefruit. If it’s difficult to inflate, stretch the material a few times or ask an adult to help you.
  2. You will need an extra set of hands for this portion. Ask your partner to hold the neck of the balloon closed to keep the air in while you insert the lens into the opening. The lens will need to be inserted perpendicularly to the balloon’s neck. It will prevent any air from escaping once it’s in place. Like your eye, light will enter through the lens and travel toward the back of the balloon.
  3. Hold the balloon so that the lens is pointing toward you. Take the lens between your thumb and index finger. Look into the lens into the balloon. You should have a clear view of the inside. Start to twist the balloon a little and notice that the neck gets smaller like your pupils do when exposed to light. Practice opening and closing the balloon’s “pupil.”
  4. Have an adult help you put the candle on the table and light it. Turn out the lights.
  5. Put the balloon about 20 to 30 centimeters away from the candle with the lens pointed toward it. The balloon should be between you and the candle. You should see a projection of the candle’s flame on the back of the balloon’s surface. Move the balloon back and forth in order to better focus the image on the back of the balloon and then proceed with data collection.
  6.  Describe the image you see on the back of the balloon. How is it different from the flame you see with your eyes? Draw a picture of how the flame looks.
  7. The focal length is the distance from the flame to the image on the balloon. Measure this distance and record it.
  8. What happens if you lightly push down on the top of the balloon? Does this affect the image? You are experimenting with the affect caused by near-sightedness.
  9. To approximate a farsighted eye, gently push in the front and back of the balloon to make it taller. How does this change what you see?

What’s going on?


Okay, let’s discuss the part of the balloon that relate to parts of your eye. The white portion of the balloon represents your sclera, which you may have already guessed is also the white part of your eye. It is actually a coating made of protein that covers the various muscle in your eye and holds everything together.


Of course, the lens you inserted represents the actual lens in your eye. The muscles surrounding the lens are called ciliary muscles and they are represented by the rubber neck of your balloon. The ciliary muscles help to control the amount of light entering your eyes.


The retina is in the back of your eye, which is represented by the inside back of your balloon. The retina supports your rods and cones. They collect information about light and color and send it to your brain.


Exercises


  1.      How does your eye work like a camera?
  2.      How can you tell if a lens is double convex?
  3.      What is the difference between convex and concave?
  4.      Can you give an example of an everyday object that has both a convex and a concave side?
  5.      How can you change the balloon to make it like a near-sighted eye?
  6.      How can you change the balloon to make it like a far-sighted eye?

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Comments

13 Responses to “Eyeballoon”

  2. Cindy Soderlund says:

    Hi. Where can I buy biconvex plastic lens and a votive candle? Thanks!

  3. The reason it’s upside down is due to the shape/focal length of the lens, not the material it’s made of.

  4. Adilah Muhammad says:

    Does it matter if the lens is plastic or glass? We used a glass lens and the candle appeared upside down.

  6. Glenn Sanders says:

    Hi there. Any suggestions on where to get the lens? Thanks!

  7. Yes, my team send you a private email when you first asked about the problem… I’ll have them contact you again. You can email us directly at [email protected] if you don’t see their email to you (check your spam folder).

  8. Maximilian Mohun says:

    its still not working and i need to start science soon… not meaning to nag or anything but have you found out whats wrong yet?

  9. I am sorry you’re having account trouble! I’ll have my team connect with you right away to get this worked out.

  10. Maximilian Mohun says:

    hi aurora! i did this experiment before so i know i have access, but now it is saying its for 9 + grades? in fact, it is saying that for everything! i dont know whether this is a glitch on the part of my computer but its very annoying as i cant access ANY experiments now. if you can help me i would be very grateful.
    thank you!

  11. Kris Smith says:

    Hi Aurora, This expirement is very cool but where can we get the biconvex plastic lens.

    Thanks for the great program, Zachary

  12. What a creative question! You are thinking really thinking like a scientist, which is great. Let’s start off with a little on how the eye works. Light goes through the cornea (outside part of your eye) and is projected onto the retina, which is kind of like a TV screen in the back of your eye. A message gets sent to the brain, which interprets it, and we can “see” something. If the retina becomes damaged, the person can’t see as well, and in some cases can’t see at all. Now, what your talking about is artificial vision. There have been some experiments, with some success, involving restoring vision in those with damaged retinas. The process involves artificially sending messages to the brain, the way the retina does in someone who can see. Here’s a great link with lots more information: http://science.howstuffworks.com/innovation/everyday-innovations/artificial-vision.htm. Keep having those big ideas!

  13. Hi, my name is Angeline, I’m thirteen and I emailed you once last year. I have a question about something and I needed someone with an open mind and a knowledge of science. Not an easy thing to find so I thought of you. This will have a lot of gaps but I needed a place to start.
    So anyway, I was wondering if we’ve figured out how the pupil works (that’s the black thing in your eye that let’s you see, right?) because if we have we could put the technology into something like swim goggles, then they could see in maybe in distance or shadows or heat vision, at least,. The goggles would either attatch into the brain, I have no idea how that would work, or, more realistically, send something like radio wave or something that the brain could understand. it wouldn’t to go very far and shouldn’t, just enough to get to the brain. It’s obvious that if that part of that brain was filled up with something else this would be useless, but if it were a new born or they just lost there vision I think it would be worth a shot.
    What do you think?
    Thanks, Angeline.