Spectrum Lab
Essential Question: How can you use a spectroscope to determine the
composition of unknown light sources?
Hypothesis: If I use a spectroscope to find the spectrum of a gas then….
Introduction: Most people believe that the telescope is the only way to
study the stars. But a very important tool to astronomers is the
spectroscope. This instrument can tell the astronomer what the
composition of a star is as well as the Doppler shift. In this lab you will be
determining the spectrum of simulated stars.
When you look at sunlight through a prism or diffraction grating, the
resulting spectrum of light is unique to sunlight. Different types of light like the neon and fluorescent light result in
different spectra because of the different gases present. Likewise, galaxies and stars are composed of different
elements so their spectra reflect the types of gases present in those objects.
There are 3 types of spectra seen in a spectroscope:
continuous
all of the colors of the spectrum are present, continuous and blend from one color to another. Like
a rainbow. This spectra is produced from HOT, glowing SOLIDS.
emission
a series of individual colored lines on a black background. This spectra is produced from HOT
glowing GASES
absorption
a continuous spectrum with portions missing. This spectra is produced from COOL glowing GASES
Materials: spectroscope, diffraction glasses, colored pencils
Procedure:
1. Copy down the data table below on to your own paper.
2. Observe each source below through the spectroscope.
3. Draw what you see, using colored pencils in the chart below.
Source
Incandescent
light bulb
Spectrum
Fluorescent
vapor tube
Compact
Fluorescent
Hydrogen
Helium
Mercury
Neon
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QUESTIONS:
1. Explain what a spectroscope does.
2. Which spectrum was:
continuous:
emission:
absorption:
3. Which light source was burning hot solids?
Explain how you determined this.
4. Which light source was burning hot gases?
Explain how you determined this.
5. Which light source was passing through a cool gas?
6. Write (or color) the order of the spectrum from shortest to longest wavelength.
longest wavelength
shortest wavelength
7. Write a short paragraph that explains what information a spectroscope may give astronomers.
Conclusion: Use your rubric
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