What is needed
What to do
Here is a picture of the final spectroscope.
Take one of the sheets of card stock and fold it in half long ways. Cut the sheet of card stock in half along this line. When you have finished you will have two sheets of card stock each one 4 1/4 " by 11". Tape these two sheets together with 3" overlapping long ways. This will give you one long sheet of card stock that is 4 1/4" wide and 19" long. Now take your scissors and cut a notch in this card stock. The notch should be 1/4" wide and 1 1/4" high. Make this notch exactly 1/2 of the distance from either end of the card stock.
Now, take the CD that you have (Fizzy Fuzzy Big and Buzzy by the Refreshments works the best, but please substitute other music according to your own taste) and hold it in your hand by the edges. Look carefully at the side that doesn't have any writing on it. This is the side with all of the encoded information. Tilt the CD back and forth in the light that is in the room. Do you see any rainbows?
While holding the CD with the information/rainbow side up wrap the long card stock around the CD. What you are trying to do is to make a little container like an open coffee can with the card stock as the sides and the CD as the bottom. The notch that you have cut into the card should be at the bottom of the container as shown in the first picture. You are going to use this notch to view the information/rainbow side of the CD. Tape the card stock into the form of a tube that it is now in. Also fasten the CD to the card stock tube with two pieces of tape. Make sure that you are putting the tape on the writing side only. If you put tape on the information side, you may damage the CD.
To finish your spectroscope, cut out a square from you other 8 1/2 by 11" piece of card stock. The square that you cut should be 5 1/2" by 5 1/2". Cut a slit about 2 mm wide and parallel to one of the sides of the square. Center the slit on one of the sides of the square and make it 1/2 inch from the edge (see picture).
The final step in building your CD spectroscope is to place this square directly onto the top of your open tube and CD container. The only thing to be careful of is to make sure that the slit is directly over the notch in the tube. See the first picture. Tape the top onto the tube.
You now have a finished CD spectroscope. The way to use it is to hold a light source up to the slit on the top, and look inside the container through the notch. You should see a very clear strip of rainbow color running from the center hole of the CD to the notch. Move the light source around to see what angle gives the best spectrum.
Try other sources of light. Different light has different color strengths. If you have trouble seeing the spectrum of some specific light, try going into a dark room and having the light you are testing being the only light.
What is happening
A spectroscope is a device that separates light into its component colors. The way a spectroscope does this is to make use of something called a diffraction grating. Light reflects and refracts through this diffraction grating, and the different colors of the spectrum all reflect and refract a little differently. This is how the colors are separated into the colors of the rainbow.
A compact disk (CD) contains a large amount of information encoded onto its surface. This information is stored in concentric rings to that it can be read by a laser beam while the disk is spinning. These concentric rings can act as a diffraction grating if the light hits them just right. You see how this works when you build a spectroscope with a CD.