## PHYS 317 - Reading Assignment #17

**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.

Back to the PHYS 317 home page.