For Balmer series lines to show up strongly in absorption in stellar spectra, significant numbers of hydrogen atoms must have electrons in the n = 2 energy level. What then does the appearance of these lines in a stellar spectrum describe about the temperature of the star's surface?
A) The appearance of the lines describes very little about the temperature because hydrogen gas will show significant Balmer absorption, whatever the surface temperature.
B) The temperature must be high enough to ionize the hydrogen atoms by collision so that they can absorb from this level.
C) The temperature must be reasonably low so that no atoms will have electrons excited beyond this energy level .
D) The temperature must be reasonably high to excite the electrons to this level by collisions but not high enough to ionize the atoms.

Question

Quizplus · Accepted Answer

For Balmer series lines to be prominent in absorption, the star's surface temperature must be in a specific range. It needs to be high enough to excite hydrogen atoms' electrons to the n = 2 level but not so high that the atoms are ionized, which would prevent the absorption of light at the wavelengths of the Balmer series.

For Balmer Series Lines to Show Up Strongly in Absorption