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Physics 404: Final Exam
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"I pledge on my honor that I have not given or received any unauthorized assistance on this examination."
May 20, 2008
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Don't get bogged down on any problem you find difficult.
Skip ahead and go through all 4 pages,
then come back to it afterwards!!
If you find a question ambiguous, ask or write a short explanation
of why.)
Much of the reference information at the end should be of help.
1. a) Show that the peak of u
(vs.
) for blackbody radiation satisfies e
x
(n-x) = n, where x
≡
/k
B
T;
be sure to identify the value of n.
b) What is the ratio of the power radiated by a sphere at T
2
compared to that of another at T
1
,
assuming all else is the same for the two spheres?
d) If the spheres have different radii R
1
and R
2
, for what ratio R
2
/R
1
is the power radiated from the
two spheres the same?
(Or will the power ratio remain the same as in (b)?)
2. A 2-state system has energies E
0
= 0 and E
1
> 0.
a) What is the ratio of occupations N
1
/N
0
?
b) What is the mean energy U?
c) What is the free energy F?
d) For a process described by the Einstein A coefficient, is a photon emitted or absorbed, and what is
its energy?
3. a) What is the entropy associated with putting a red, a green, and a blue ball into 5 bowls? (no more
than one ball per bowl)?
b) What is this entropy if the balls are the same color (indistinguishable)?

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*Sign up*4. Consider the chemical reaction
2CO + O
2
↔
2CO
2
a) What is the relationship (in equilibrium) between the chemical potentials of the 3 gases?
b) What is the equilibrium constant
K
in terms of the partial pressures of the 3 gases?

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