The atmosphere of a DB white dwarf is pure helium. Use Saha's equation to calculate the ionization ratios NII/NI and NIII/NII for temperatures of 5,000 K, 15,000 K, and 25,000 K. Express NII/Nt (Nt = total number of ions) in terms of these ratios and plot NII/Nt for temperatures from 5,000 K to 25,000K. Determine the temperature at which half the helium is ionized.
For more information on how to do this problem, and for tables of relevant data, see
www.canismajor.ca.