Why Is There a Limited Range of Stellar Surface Temperatures

question 156

Multiple Choice

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 n = 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.

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