What's a Spectroscope?
You look into the sky and see the beautiful sun and the stars. Were you aware that you can learn more about the composition of the sun and the stars by using an instrument called a spectroscope? Yes, it is most certainly possible! In fact, this instrument can be used to determine the composition of other items, such as a planet or even a light bulb.Spectroscopes are instruments that allow scientists to determine the chemical makeup of a visible source of light. The spectroscope separates the different colors of light so that scientists can discover the composition of an object. Now, to really understand how this instrument works, we need to review basic concepts of white light and its relation to color.If we focus on light in general, we will see that it consists of distinct wavelengths. A wavelength is the distance between two crests or troughs. Each color in light corresponds to a wavelength. Our friend, white light, just so happens to contain all of the colors (or the entire spectrum) of visible light. Examples of white light include our pals, the sun and the stars.What happens when you take a spectroscope and place it in the presence of white light? Great question! When the spectroscope comes into contact with white light, it splits, or diffracts, the light into all of its colors. This causes each of the colored beams to point in a different direction, allowing you to view each color as a single narrow band. This band is often viewed as a dark line called the absorption line.Recall that a spectroscope allows us to determine the atomic makeup of visible light sources. When an atom gets excited or happy, it emits light. This emission of light corresponds to a signature spectrum we call an atomic spectrum, which is a spectrum made from a group of colored lines that are formed when atoms become excited and emit light. By comparing this signaturespectrum to the absorption lines viewed by a spectroscope, we can learn about the chemical makeup of an object. Let's say we take the sun and decide to study the composition of it by using a spectroscope. We determine the spectrum of the sun as shown in the illustration.The dark lines, or absorption lines, we see from the spectroscope can be compared to known atomic spectrums. From this comparison we discover that the sun containsthe atoms hydrogen, sodium, and magnesium. Although an example, you can see that the spectroscope can be quite useful when the need arises to learn more about the chemical makeup of material, such as that of the sun.What are the different ways a scientist can use the spectroscope to learn about the composition of light source materials? Well,
they can learn by measuring one, or all, of the following:• The actual color of light that is distinctly observed
• The color of light that is reflected
• The color of light that is absorbed
Now that we have defined a spectroscope and understand its importance in science, let's take a look at the different parts used to make this instrument. Parts of a Spectroscope
There are different parts of the spectroscope, all of which are necessary for the instrument to function properly. Here's an illustration highlighting the main parts of a spectroscope:
Make a truth teller for light.
Turn an old CD into a spectroscope to analyze light—you may be surprised by what you see. Try pointing your CD spectroscope at the fluorescent light in your room, sunlit clouds in the sky, even your friend’s colored shirt to reveal the wavelengths of light that mix together to create the color you see!
Tools and Materials
A compact disc (CD). A cardboard tube that's at least 12 inches long (approximately 30 centimeters) and 3 to 4 inches (7.5 to 10 centimeters) in diameter, Two covers for the cardboard tube—we suggest two flat pieces of cardboard large enough to cover each end of the tube, or you can also use the plastic covers that come with a cardboard packing tube, Razor knife such as an X-ACTO knife, Tape, Access to fluorescent light, Saw, Cutting guide (scaled for a 3-inch