Question

Why is there a limited range of stellar surface temperatures around 10,000 K at which neutral hydrogen gas absorbs visible light in the Balmer series?

A) There must be electrons at the n = 3 energy level for Balmer absorption to occur. If the gas is too cold, electrons are only in the n = 1 and 2 levels; if the gas is too hot, the gas is ionized and no electrons are left in the hydrogen atoms.
B) Electrons in hydrogen have to be at the n = 2 energy level to produce absorption in this series. If the gas is too cold, most atoms are in the n = 1 state; if it is too hot, most atoms are ionized.
C) Electrons must be in the ground state n = 1 to undergo Balmer absorption. If the gas is too cold, electrons cannot be excited from this level; if the gas is too hot, there are no electrons left in the n = 1 level.
D) There must be sufficient continuum radiation from the stellar surface in the visible region to be absorbed by the hydrogen gas.

Answer 1

The limited range of stellar surface temperatures around 10,000 K for Balmer absorption of visible light in neutral hydrogen is due to electrons needing to be in the ground state (n = 1).

Step-by-step explanation:

The limited range of stellar surface temperatures around 10,000 K at which neutral hydrogen gas absorbs visible light in the Balmer series is due to the requirement for electrons to be in the ground state (n = 1) to undergo Balmer absorption. If the gas is too cold, electrons cannot be excited from this level. If the gas is too hot, there are no electrons left in the n = 1 level. Therefore, at temperatures around 10,000 K, there is a significant number of hydrogen atoms excited to the second energy level (n = 2) which allows them to absorb photons and produce the dark absorption lines in the Balmer series.