What does absorbance measure in a spectrophotometric analysis?

Absorbance in spectrophotometric analysis specifically measures the amount of light that does not pass through a sample, effectively reflecting how much light has been absorbed by the sample itself. When light is directed at a sample, some portion of that light is absorbed, and the remaining light either gets transmitted through or reflected off the sample. The absorbance is quantitatively determined using the logarithmic relationship based on the intensity of light entering the sample compared to the intensity of light emerging from the sample.

This measurement is essential because it provides insight into the concentration of substances within the sample, following Beer-Lambert law, which states that absorbance is directly proportional to concentration. Thus, understanding absorbance allows for the analysis of solutions, particularly in fields such as biochemistry and environmental science.