Nuclear & Particle Physics - EM Spectrum

A spectral line is produced by a gas that is sufficiently dense that the mean time between atomic collisions is much shorter than the mean lives of the atomic states responsible for the line. Compared with the same line produced by a low-density gas, the line produced by the higher-density gas will appear

A. The same
B. More highly polarized
C. Broader
D. Shifted toward the blue end of the spectrum
E. Split into a doublet

(GR8677 #83)

Solution:

Spectral lines = bright or dark lines correspond to the emission or absorption of light of a single wavelength.

High-density gas:

• Atoms experience frequent collisions and many other mechanisms that cause spectral lines to lose their sharpness.
• It produces a continuum spectrum = weaker, less distinct or broader spectral lines.

Low-density gas:

• Atoms do not experience many collisions (the energy is coming from the particles themselves).
• It produces sharp spectral lines: emission spectrum (by hot low-density gas) and absorption spectrum (by cold low-density gas).

Answer: C