A rainbow is nature's prism on a grand scale. A typical prism is a triangular piece of clear glass or plastic that bends light as it passes through the prism's apex.

Light slows down as it passes from the air into the denser material of the prism. Different wavelengths of visible light bend at different degrees; violet light bends the most as it passes through the prism and red light the least. It was Isaac Newton who realized that white light was actually made up of the spectral colors of the rainbow.

• 	This setup uses a flashlight and dark-colored paper so that it's easier to see how the prism bends light.

  A prism (or two)
• A cardboard box (such as a file box)
• Colored pencils or pens
• A sheet of plain white paper
• A flashlight or reading lamp

In order to create a clearly visible spectrum of light with a prism, it's best to work in a darkened room with a single source of light. A cardboard box (such as a file box) makes a great prism box. Simply cut a small rectangular opening on the side of the box near the bottom edge, about 5 mm in width.

Inside the box, place the prism on a sheet of dark paper. Shine the flashlight beam through the hole and adjust the prism as shown in the photograph. Use colored pencils or pens to trace the individual bands of light that you see. In what order are the colors? Can you come up with a mnemonic to help you memorize the sequence of colors in prismatic light?

Finally, cut a second hole in the box and arrange two prisms so that their spectra cross paths. What happens to the various colors of light where they cross?

If you are interested in owning a prism of your own, you can purchase prisms from science education and nature stores. You can also find great prisms inside of some kinds of binoculars (ask an adult if they have a broken pair lying around – but ask first before you begin to dismantle them). If you can't have the real thing, you can still create the prismatic effect with a variety of objects. Try some of the following:

• Create the prismatic effect with crystals from a lamp or piece of jewelry. (Again, ask an adult first.)
• Create a water prism using a clear glass or jar filled with water (a square jar or small fish tank works best). Place the container in a well-lit window of a room that is otherwise fairly dark. By moving the container around, you can cause a prismatic effect on the opposite wall of the room.

• 	What color is a Blue Jay really? Find out by reading this quick story.

  Place a bowl of water in a sunlit window and hold up a small mirror at an angle in the water. By adjusting the mirror (a potentially tedious process!) you should be able to create a prism on the wall.
• A simple compact disc will create the prismatic colors of the rainbow if you look at the surface under bright light. The thousands of tiny grooves on the surface of the CD cause the light to split into its component colors in a process called diffraction. Although the light isn't being bent as with a true prism, the grooves are teasing out and reflecting various colors of the spectrum.

What else can you find lying around in the house to create a prism? If you run out of ideas, you can also go outside on a hot summer day and create a fine spray with a hose. The result is your own rainbow, complete with rain!