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{\bf Introduction to Astrophysics I, 29:119\\
     Fall, 2006\\
Seventh Homework Set...November 3, 2006.\\ Due November 9, 2006}\\
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Show calculations and give reasons for your answers. Don't go around 
confused and despondent; if you do not know how to get started, ask me for help. All problem numbers refer to the first edition of the book.\\


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{\bf (1)} In a Maxwellian distribution, what fraction of the atoms have an energy at least 20 times that of the mean energy?  Explain what you are doing to calculate this number.  \\

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{\bf (2)} Assume that at a given point in the solar atmosphere, emission lines of Si III  and Si IV are about equally strong, leading you to conclude that there are equal numbers of Si III and Si IV ions in the atmosphere.  What is the temperature at this point in the Sun's atmosphere?  {\bf Hint:} Look at Figure 8.9.  \\

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{\bf (3)} A star has prominent absorption lines of neutral helium and Si III, weak but visible lines of singly ionized helium, and weak lines of neutral hydrogen.  At what wavelength is the continuum light from this star brightest? {\bf Hint:} Look at Figure 8.9.  \\ 

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{\bf (4)} Problem 8.5 from book.\\

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{\bf (5)} Problem 8.6\\

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{\bf (6)} Problem 8.7\\

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{\bf (7)} Problem 8.9\\

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{\bf (8)} Problem 8.10\\




 
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