I just built a DIY spectroscope using a CD and after making some tests, I noticed a really strong emission line located in the orange-yellowish zone of the fire spectrum (specifically, burning wood).

I think that the strong line could be actually sodium, but wouldn't that mean that wood contains a lot of sodium in order to see such a strong emission line?

  • 2
    $\begingroup$ There's a related question on the Physics site about orange colour in a gas flame. There's some blackbody radiation, but the consensus is that the yellow lines are sodium. It doesn't take much salt to produce those lines. $\endgroup$
    – PM 2Ring
    May 10 '19 at 0:16
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    $\begingroup$ It's sodium. It's everywhere. This is why a lot of natural fires skew orange-yellow - it's the sodium pulling the color towards the yellow region. Even trace amounts will make that line, you don't need a ton of it. BTW, the line is a doublet, you can see it if your device has good spectral resolution. $\endgroup$ May 10 '19 at 3:29
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    $\begingroup$ Congratulations on building your own DIY spectroscope! I propose you try to snap a photo through it and add it to your question, real data rocks! You might also see if adding a little salt or baking soda (sodium bicarbonate) to the fire enhances the yellow line. You also might consider moving your question to Chemistry, Physics, or Biology Stack Exchanges if people close your question here. If you can mention that you are truly interested in looking at spectra of planets or stars or the Moon next, that would keep your question on-topic here. $\endgroup$
    – uhoh
    May 10 '19 at 3:48
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    $\begingroup$ FWIW, you can probably also see a violet line from potassium. Traditionally, potassium hydroxide was made from wood ash. And sodium hydroxide from seaweed ash, which as you might guess has a lot of salt. ;) $\endgroup$
    – PM 2Ring
    May 10 '19 at 4:20
  • $\begingroup$ Throw some salt on the fire to confirm. $\endgroup$ May 12 '19 at 14:41

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