Make a lens and see how your eye manipulates the light that enters it.

• Utility or Exacto knife

• Clear glass

• Water

• Scotch tape

• A piece of colored plastic

• Flashlight

• Shoebox or similar box, no top needed

1. Carefully cut 2 vertical slits in one end of the box—you may want an adult to help you. The space between the slits should be smaller than the width of the glass.
2. Place the colored plastic over one of the slits, and tape it in place.
3. Turn on your flashlight and darken the room.
4. Shine the flashlight into the box through the slits.
5. Look inside the box. What is the light doing? Where do the light rays appear on the side of the box?
6. Pour water into the glass, and place it in the center of the box. Repeat steps 3 and 4.
7. What happens to the light beams after they pass through the glass of water?

The box is a model of your eye. Light enters through the opening in the front of your eye (the iris) and passes through a crystalline lens. The lens focuses the light into an image that falls on your retina (the inside of the back of your eye). When an image falls on the retina, nerve cells send signals to your brain which are interpreted to create an image.

Want to Learn More? Read an article related to this activity:

• The Refraction of Light

To find this experiment and many more please download the Lighten Up! Discovering the Science of Light book, developed through a partnership with the Optical Society of America’s Foundation (OSAF) and the Girl Scouts of the USA.