Answer Happy

Assuming that a stellar atmosphere is fully ionised explain what is the mean molecular weight, H, and why is it needed. Show how we define this parameter, starting with the number density of nuclei per unit volume and determine the mean atomic weight of the plasma, ul. Show how things change including electrons as well. What is the mean molecular weight in the case of pure hydrogen plasma, and in the case of a pure He plasma. For the Sun, give the mean molecular weight, showing how you get this number