The Sodium D Lines Are a Closely Spaced Pair of Spectral

question 212

Multiple Choice

The sodium D lines are a closely spaced pair of spectral lines in neutral sodium. They are present as absorption lines in the spectrum of the Sun's photosphere because of traces of sodium there. What would one expect to see if sunlight is passed through a cool sodium vapor in the laboratory and then observed with a spectroscope?

• A) The sodium D lines will become brighter.
• B) The sodium D lines will become darker.
• C) The two absorption lines will merge into a single line.
• D) The position of the sodium D lines will shift to a lower frequency.

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