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 you 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) No change in the sodium D lines will result.

Question

Quizplus · Accepted Answer

When sunlight is passed through a cool sodium vapor in the laboratory, the sodium atoms in the vapor will absorb some of the light at the same wavelength as the sodium D lines. This will result in a decrease in the intensity of the sodium D lines, making them appear darker in the spectrum observed with a spectroscope. Therefore, option B is the correct choice.

The Sodium D Lines Are a Closely Spaced Pair of Spectral