In a assignment problem, I had to calculate the relative number of hydrogen atoms in the fundamental state, first, second and third excited states for a temperature of 5000 K. I used Maxwell-Boltzmann's statistics and I found out that (from memory) the most populated state was the fundamental one. The first excited state was much less populated, by a factor of 10^-10 compared to the fundamental state. The 2nd excited state about 10^-12 compared to the fundamental state (thus about the order of 100 times less populated than the 1st excited state) and so on. The next question was "explain why the Balmer series dominates over the Lymann series for the absorbtion spectrum of the Sun". I've checked out in a book and it stated that one has to assume that any transition is approximately as likely probable as any other. Thus I do not have any idea on why if the fundamental state is the most populated, the Lymann series doesn't dominate. As far as I remember the Lymann series is due to any transition up to the fundamental state, i.e. n--> n=1. Why would a series with n-->n=2 be more intense than the Lymann's one?! I'm totally stuck on this. This has nothing to do with the atmosphere (the problem specified this hold true even if we watch the Sun from space) or the Earth. I'm totally at a loss. It's not really homework even though it was asked as an assignment more than 1 month ago. The question is haunting me.