Atoms and Starlight
Review Questions
1. Why might we say that atoms are mostly empty space?
3. Why is the binding energy of an electron related to the
size of its orbit?
5. Describe two ways an atom can become excited.
6. Why do different atoms have different lines in their spectra?
8. Why do hot stars look bluer than cool stars?
10. Why are Balmer lines strong in the (absorption) spectra of medium
temperature stars and weak in the (absorption) spectra of hot and cool stars?
11. Why are titanium oxide features visible in the spectra of only the
coolest stars?
15. Explain why the presence of spectral lines of a given element
in the solar spectrum tells us that the element is present in
the Sun, but the absence of the lines would not mean that the
element was absent from the Sun.
Problems
1. Human body temperature is about 310 K (98.6o F).
At what wavelength do humans radiate the most energy? What kind
of radiation do we emit?
2. If a star is five times hotter than the Sun, how much more energy
per second will it radiate from each square meter of its surface?
At what wavelength will it radiate the most energy?
3. Transition A produces light with a wavelength of 500 nm.
Transition B involves twice as much energy as A. What wavelength
light does B produce?
Last update: February 16, 1998.
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