[blazinfury]

Which of the following colors would appear as a bright band in an emission spectrum of a yellow sodium vapor lamp?


B. Yellow, indicating a greater wavelength than ultraviolet light
A. Yellow, indicating a lesser wavelength than ultraviolet light
C. Blue, indicating a lesser wavelength than ultraviolet light
D. Blue, indicating a greater wavelength than ultraviolet light

The answer is (B).

I just feel like it was a bad question because I did not know whether the band would appear yellow or blue. Just because Na appears yellow does that mean that yellow is the color that it emits and so on a spectrum it will appear yellow as well?

I understand that this problem deals with the ideas of emission and reflection. The sodium reflects the yellow color, but does it emit it as well? If so, since light particles (photons) are constantly bombarding it, exciting it, and then when Na goes back to ground state it emits a color.

[swansont]

blazinfury, on 10 January 2012 - 04:52 AM, said:

Which of the following colors would appear as a bright band in an emission spectrum of a yellow sodium vapor lamp?


B. Yellow, indicating a greater wavelength than ultraviolet light
A. Yellow, indicating a lesser wavelength than ultraviolet light
C. Blue, indicating a lesser wavelength than ultraviolet light
D. Blue, indicating a greater wavelength than ultraviolet light

The answer is (B).

I just feel like it was a bad question because I did not know whether the band would appear yellow or blue. Just because Na appears yellow does that mean that yellow is the color that it emits and so on a spectrum it will appear yellow as well?

I understand that this problem deals with the ideas of emission and reflection. The sodium reflects the yellow color, but does it emit it as well? If so, since light particles (photons) are constantly bombarding it, exciting it, and then when Na goes back to ground state it emits a color.

Sodium has a doublet near 589 nm. The problem stated that this is emission, so it will emit this light. A sodium vapor lamp does not rely on photon absorption for the excitation — it's an applied field that causes excitation/ionization.