Sodium Absorption Lines
Burning of sodium bicarbonate in Bunsen flame produces sodium absorption lines in continuous spectrum. Sodium 'D' line absorption shows up as a black line in the yellow of a continuous spectrum. Good as a simulation of the sodium portion of the Fraunhoffer absorption spectrum caused by atoms in the solar atmosphere; it does not however, resolve the 5890/5896Å doublet.
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http://sciencedemonstrations.fas.harv...