\documentstyle[11pt]{article}
\textwidth 14.0cm
\oddsidemargin 0pt
\evensidemargin 0pt
\begin{document}
\begin{large}
\begin{center}
{\bf Introduction to Astrophysics I, 29:119\\
     Fall, 2008\\
Eighth  Homework Set...November 4, 2008.\\ Due November 11, 2008}\\
\end{center}
\end{large}
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.\\


\noindent
{\bf (1)} Problem 9.13 from textbook \\

\noindent
{\bf (2)} Problem 9.22 from textbook \\

\noindent
{\bf (3)} Problem 9.23 from textbook  \\ 

\noindent
{\bf (4)} Problem 10.1 from textbook \\

\noindent
{\bf (5)} Problem 10.3 from textbook\\

\noindent
{\bf (6)} Assume that the solar photosphere is {\em isothermal}, i.e. that its temperature is constant.  Calculate the {\em pressure scale height} in the photosphere, i.e. the vertical scale length over which the pressure falls by a factor of $e$.  {\bf Hint:} You have to search in the textbook for some important numbers. \\

\noindent
{\bf (7)} Compare the pressure gradient in the photosphere with the {\em maximum} pressure gradient in the interior of the Sun.  {\bf Hint:} Information on conditions in the interior of the Sun are available in your textbook, and elsewhere.\\

\noindent
{\bf (8)} Use the chemical abundances of the Sun in Table 9.2.   Demonstrate the truth of the statement in the textbook (p293) that 
\begin{equation}
\left< \frac{1+z}{A}\right>_i \simeq \frac{1}{2}
\end{equation}\\

\noindent
{\bf (9)} Given the result from problem \# 8 and the data in Table 9.2, calculate the mean molecular weight for fully-ionized solar material. \\

\end{document}
