Glowing Eyes

What You Need: 

• Two clean cans such as mandarin orange cans 
• Black construction paper
• Red construction paper
• Scissors
• Masking tape
• Aluminum foil
• Flashlight

What You Do:

1. Why does your young scientist think that a cat’s eyes glow at night? Explain that you are going to make two models to test this. One model will be of a cat’s eye and the other of a human eye.
2. Be careful with this next step. Some cans have sharp edges. Trace one of the cans onto the red construction paper. Cut out the circle. Slip the red construction paper into the base of one can. This will be the human eye. The paper represents the blood vessels and retina at the back of a person’s eye.
3. Using the can as a guide, draw a circle that is slightly larger than the base of the can on the black construction paper. Cut this circle out and then carefully cut a round circle, the pupil, from the center. Center this iris and pupil on top of the can. Secure with several pieces of masking tape.
4. Now it is time to make the model of the cat’s eye. Use a piece of aluminum foil to line the base inside of a second can. Make sure the shiny side is up. 
5. Cut a second circular iris from black construction paper. From the center, cut out an oblong circle that looks like a cat’s pupil. Center this on top of the second can and tape into place.
6. In a dark room, shine a flashlight at both models. Which one seems to glow? If the cat’s eye model doesn’t reflect the light, the can might be too deep.  Wad up a paper towel and stuff it into the can. Now wad up a piece of foil and put it on top of the paper towel. Tape the pupil back into place. Shine the light at the model and it will reflect light because the light bounces off the foil. In a real cat’s eye, a membrane called the tapetum lucidum reflects light to hit the light receptors in the cat’s eye. This helps the cat see in the dark.