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As the days get shorter and the nights get longer, we could all use a little more light and color in our lives. And you can explore the colors contained in light by creating a real science instrument – a CD Reflective Spectroscope.

Scientists use special instruments that help them understand the universe, galaxies, stars, and planets. An important tool used to gather information about these objects is called a spectroscope. The scientific technique that utilizes the spectroscope is called spectroscopy.

Objects made up of hot gasses (like a light bulb or a star) and objects with cool gasses (like the atmosphere around a planet) give off different light colors, depending on the chemicals in the gasses. So, since chemicals produce or reflect different color lines (as seen through a spectroscope), scientists are able to determine what kinds of chemicals are present – even from stars that are billions of light-years away!

Concept:

A spectroscope is a device that separates light into its component colors. It does this by making use of something called a diffraction grating. As light reflects through this diffraction grating, each color of the spectrum reflects a little differently. This is how the colors are separated into the seven colors of the rainbow (red, orange, yellow, green, blue, indigo and violet).

This CD displays the spectrum of incandescent light

A compact disk (CD) contains a large amount of information encoded onto its surface, information stored in concentric rings so that it can be read by a laser beam while the disk is spinning. These concentric rings can act as diffraction grating when light hits them just right, and can separate the colors. You will see how this works when you build your Reflection Spectroscope with a CD.

(Image right shows a slice of a CD under the a microscope)

Objective:

To separate and observe the array of colors in the visible spectrum and how those colors change, depending on the chemicals in the light source.

Materials:  

1. A shoebox with a lid

2. Scissors and tape

3. A metric ruler

4. A blank CD

5. Various light sources (fluorescent light, incandescent light, candle, etc.)
    

Procedure:

1. A CD Reflective Spectroscope is made from of a CD mounted diagonally at the end of a shoebox. The figure below shows how the spectroscope is made.

2. The CD may be held in place with either a small piece of tape or by inserting it into a slit cut in the bottom of the shoebox.

3. A second narrow slit, approximately 5-cm long and 5-mm wide, is cut in the shoe box lid. Directly over the CD, this aperture admits the light to be analyzed.

4. At the opposite end from where the CD is mounted, a viewing window, roughly the size of a postage stamp, is cut in the shoebox’s end panel.

5. Trial and error should be used when positioning the angle of the CD, until the best spectral display is provided.

6. While looking through the viewing window, lean the box down, so the light from the source (lamp, candle, etc.) enters through the hole in the top. You will see the color lines reflected off the surface of the CD.
    

Questions:

Do different light sources produce a different spectrum?

Different sources of light produce different colors when viewed through your CD Reflective Spectroscope. Try a regular light bulb (which is incandescent light), a fluorescent light, a black light, an LED light, computer monitor, candle light (just be careful!!), or the moon. If you have difficulty viewing the spectrum of a specific light, try going into a darkened room and have the light you are testing be the only light source in the room.

Do different light sources have anything in common?

Although the chemicals in each light source are different, you will see that some colors are seen in almost all of the spectra.  That is because there are similar chemicals that are used in many different kinds of light bulbs, and also many of the same chemicals that appear in a spectroscope when it separates the light from stars throughout our galaxy.

Now that you’ve broken colors apart from white light, what happens when you put colors together?

Put a glass on a piece of white cardboard. Draw around the base and carefully cut out the circle. Make a hole in the center of the card using a hole punch. Dividing the circle into three, equal-sized sections, color one blue, one red, and one green. Place the hole in the middle over the tip of a pencil and spin the card.

What colors do you see when the card spins slowly? What colors do you see when it spins very quickly?

Light reflects from each of the colors and your brain can keep them separated for a while when the card spins slowly. But, the faster the spinner moves, the harder it is for your brain to keep the colors separate. Your brain finally combines all the colors and you see a mixture of all seven colors (red, orange, yellow, green, blue, indigo and violet), which is white light. Your spinner may look a little grey to you if your red, green and blue colors are not perfectly accurate.

If you learned some interesting things about how different colors of light are given off by different sources, you might want to keep the results and your Reflective CD Spectroscope for use in a science fair experiment at school!

Do you enjoy doing science experiments and discovering new things that reveal scientific facts? If you do, you’ll want to check out www.ScienceMuseumGifts.com – where science and fun come together
 

Mirage 3D: It's more than an illusion!

If you had fun exploring some of the properties of light, you’ll love our Mirage! You’ll create three-dimensional images in amazing resolution and startling clarity! Explore the difference between reality and sensory perception.

Go there now!

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