The Luminosity classification system (Roman numerals) is based on the widths of
ID: 1997555 • Letter: T
Question
The Luminosity classification system (Roman numerals) is based on the widths of spectral lines. The observed variations in spectral line width (narrower lines for giant stars) arise from:
Doppler broadening due to faster rotation rates of giant stars.
Pressure (collisional) broadening due to the lower densities of giant stars' atmospheres.
Natural broadening due to relativistic corrections in the Heisenberg uncertainty principle in massive stars.
Temperature effects due to higher surface temperatures on giant stars.
A.Doppler broadening due to faster rotation rates of giant stars.
B.Pressure (collisional) broadening due to the lower densities of giant stars' atmospheres.
C.Natural broadening due to relativistic corrections in the Heisenberg uncertainty principle in massive stars.
D.Temperature effects due to higher surface temperatures on giant stars.
Explanation / Answer
B. Pressure broadening dye to the lower densities of giant star atmosphere
An important factor that can broaden spectral line is pressure. With increasing pressure in the stars outer layers more and more atoms will be disturbed during the time when emitting or absorbing a photon. This results in a change of energy of the level of the aim. Thus, the width of a spectral line increases as pressure increases.
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