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Chemistry · Glossary

What is Absorbance?

Definition 29.6 School Chemistry — Grades 1 to 12 · Chapter 29 — Colour and Absorbance

The absorbance AA of a solution, at a chosen wavelength, is the number displayed by a spectrophotometer that measures how much of the light of that wavelength the solution absorbs. It has no unit; it is zero for the pure solvent, and the larger the more light the solution absorbs.

Principle of a spectrophotometer. A prism spreads white light into its colours; a slit lets through only one wavelength, chosen by the user; the detector compares the light leaving the cell with the light entering it, and the display gives the absorbance.
Principle of a spectrophotometer. A prism spreads white light into its colours; a slit lets through only one wavelength, chosen by the user; the detector compares the light leaving the cell with the light entering it, and the display gives the absorbance.
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