- What does it mean for an energy level to be degenerate?
When two or more different microstates have the same energy level, then we
call this energy level degenerate (basically, knowing the energy isn't
enough to specify a unique microstate).
- What must we assume about the entropy change of the reservoir to
go from equation (6.2) to (6.5)?
We need to assume that the PdV contribution is negligible compared to the
dU contribution.
- What is the name (in words) for the sum of Boltzmann factors
over all possible states?
The partition function. Don't ask me why.
- How many hydrogen atoms out of a billion are in the first excited
state at a temperature of 5800 K?
The "first" excited state is really 4 different states [for those up on
quantum mechanics, we have (n,l,m) values of (1,0,0), (1,1,1), (1,1,0),
and (1,1,-1).] For each of those states we have a probability around
e^(-20). Multiplying by 4 gives 5.6 atoms out of a billion in the first
excited state.