Light from the Stars (Building a Spectrometer)
The instructions below describe how to build a spectrometer. Here is a link if you wish to view the site where the instructions are from: Lab, Camera, Action: Make your own CD spectrometer (Links to an external site.).
Materials needed:
• A CD or DVD that can be sacrificed to this project. Old software CDROMs work great.
• A cereal box. Any size that can hold a CD or DVD disk will do.
• A sharp knife or razor blade to cut into the cereal box.
Our spectroscope has three main parts. There is a slit made from a razor blade to make a path for the light, a diffraction grating made from a CD disk, and a viewing port.
To construct your spectroscope, you need to put a slice in one side of the box at roughly a 30-degree angle. This will hold the CD. Place the CD in the slot to determine where to place the other two cuts. On the top of the box, cut a hole about half an inch to an inch square above the CD. On the side opposite the CD, make a very narrow slit opposite the CD. Alternatively, you can cut a larger slit, and cover it with 2 pieces of foil to control the size of the slit. Spectroscope complete!
Photograph your finished spectrometer and include the photo in your lab report.
Once you have assembled your spectroscope with the instructions in the lecture and above, use it to examine the spectra of three different light sources. Make sure that at least one of them is the sun or moon, but the others can be incandescent lights, compact fluorescent bulbs, LED lights, halogen or xenon bulbs, televisions, computer screens, candles, fireplaces, etc. Aim the slit towards the light source you are investigating, then look through the viewing hole to see the spectrum on the disk.
Answer the following questions:
1. Identify each light source you viewed and describe the spectra you observed from that source. For each description, include colors, if the colors are blended together or separated, and if the colors are fuzzy or distinct.
2. What feature of the light source do the spectra represent? In other words, what is it that you are actually analyzing?
3. Why do you think spectrometers are so valuable for studying celestial objects?
