Atomic absorption is to measure the content of the components to be measured in the sample through the attenuation of radiation intensity (absorbance) after the characteristic spectral line emitted by the hollow cathode lamp passes through the atomic vapor of the sample.

In atomic absorption spectrometry, in order to make the relationship between the absorbance of the elements to be measured in atomic vapor and the number of atoms in the ground state obey Lambert-Beer law, the emission linewidth must be smaller than the absorption linewidth. If the incident light is 5- 10 times narrower than the absorption spectrum when a sharp light source is used, it can be considered as monochromatic light, and the absorbance is linearly related to the concentration, that is, A=Kc.

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