Do you know Roy G. Biv? You have probably seen him many times. Roy G. Biv isn’t a real person, but his name will help you remember the colors that make up visible light. Each letter in Roy G. Biv stands for one of the colors in a rainbow (red, orange, yellow, green, blue, indigo, and violet). A spectroscope will help you learn more about light and rainbows.
Materials: oatmeal container or a shoebox with a lid, old CD, scissors, utility knife, duct tape, clear tape
Caution: Adult supervision is required for this activity!
To Do:
Ask an adult to carefully cut a slit measuring 1/8 inch wide by 1 1/2 inches long in one end of the container.
Cut a hole measuring 1 x 1 inches at the opposite end of the container.
Place a piece of duct tape on the labeled side of the CD and press down firmly. Quickly pull the tape from the CD. You should have removed some of the silver coating from the CD along with the tape. Repeat this process until you have removed most of the label.
Use the scissors to cut a piece of the CD that is slightly larger than the opening you made in step 2.
Tape the clear CD over the larger opening on your container.
While looking through the CD, aim the slit at a light source. What do you see inside the container? Never aim it directly at the sun!
Now Try This:
Try aiming your container at different sources of light, such as an incandescent light bulb, a fluorescent light, an LED light, or even the flame of a candle. Does the pattern inside the container look different? You can also try varying the width of the slit. Does this affect the pattern that you see inside the container?
What’s Going On?
The device you made is called a spectroscope, and the pattern of colors you see inside the container is called a spectrum. Visible light from the sun is actually made up of many different colors, or frequencies, of light. When you point your spectroscope at a light source, the CD acts like a prism, spreading light into its component colors. Violet light (the highest frequency of visible light) is at one end of the spectrum and red light (the lowest frequency of visible light) is at the other. The surface of the CD contains many small grooves. When light hits the CD, these little grooves separate the colors so they reflect at different angles onto the wall of the spectroscope.
Does the pattern of colors inside your spectroscope change when you point it at different sources of light? Incandescent light bulbs and sunlight will produce a continuous spectrum, where all the colors merge smoothly into each other. A fluorescent light will produce a spectrum of bright lines separated by dark spaces. Try drawing each spectrum with colored pencils and comparing them.
Debbie DeRoma is the Education Manager at the Reuben H. Fleet Science Center.
