A star shows weak hydrogen Balmer lines but strong lines of neutral sodium. What is a likely explanation for this?
A) This particular star contains no hydrogen.
B) The hydrogen has been ionized.
C) The hydrogen is not receiving enough energy to populate the n = 2 level required for Balmer transitions.
D) The sodium lines are masking the hydrogen lines because these occur at the same wavelengths.

Question

Quizplus · Accepted Answer

The weak hydrogen Balmer lines suggest that the hydrogen is not in the n = 2 energy level, which is necessary for Balmer transitions. This is likely because the star is too cool to excite hydrogen atoms to this level, while neutral sodium lines are strong because sodium remains in a neutral state at these temperatures.

A Star Shows Weak Hydrogen Balmer Lines but Strong Lines