Sections Review

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Vocabulary

absorption line spectrum continuous spectrum discrete spectrum
emission line spectrum luminosity Stefan-Boltzmann law
thermal spectrum Wien's law

Formulae

1. Wien's Law: peak = 2.9 × 106/temperature. The units of the peak wavelength are nanometers and the temperature is in Kelvin.
2. Stefan-Boltzmann Law: Energy emitted by a square meter on an object's surface = ×temperature4, where is a constant of nature.

Review Questions

1. What are the three basic kinds of spectrum? Can an object produce more than one type at the same time?
2. What produces a thermal spectrum? Does it depend on chemical composition?
3. How can temperature be determined from a continuous spectrum? How would the color of a hot object compare to the color of a cooler object? At what wavelength do you at 98.6 degrees Fahrenheit radiate the most? (Hint: use the temperature scales table.)
4. How will the thermal spectrum produced by a chunk of lead compare to the thermal spectrum produced by a chunk of iron of the same size and temperature?
5. What produces an emission line spectrum? Do you need a thermal source in the background?
6. Can you see emission lines if a thermal source is in the background? What does their visibility depend on? (Think about the temperature of the gas producing the emission lines and the temperature of the the background thermal source.)
7. What produces an absorption line spectrum? Do you need a thermal source? Would you see absorption lines if the gas in front of a thermal source was hotter than the thermal source? Explain why.
8. Why must you use a pattern of lines to find the composition? Why is one line not sufficient?
9. What kind of spectrum and what pattern of lines would you see if you heated up a tube filled with hydrogen, helium and neon gas?

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last updated: 17 May 2001