Beers law

Beer's Law, also known as Beer-Lambert Law or Beer-Lambert-Bouguer Law, is a principle in quantitative analysis in the field of physical chemistry. It describes the relationship between the absorption of light by a substance and the properties of the substance. The law is named after the German mathematician and chemist August Beer.

Overview

Beer's Law states that the absorbance of a solution is directly proportional to its concentration and the path length of the light through the solution. This relationship is expressed mathematically as:

A = εlc

where:

• A is the measured absorbance,
• ε is the molar absorptivity (a measure of how strongly the substance absorbs light of a particular wavelength),
• l is the path length through which the light passes, and
• c is the concentration of the absorbing species in the solution.

Applications

Beer's Law is widely used in the fields of chemistry, physics, and earth science to quantify the concentration of a solute in a solution. It is commonly used in spectrophotometry, a technique for measuring light intensity.

Limitations

While Beer's Law is a useful tool, it has its limitations. It assumes that the absorbing species are independent of each other and that the medium does not scatter the light. In practice, these assumptions are not always valid, especially at high concentrations or for complex mixtures.

See also

• Spectrophotometry
• Absorption spectroscopy
• Quantitative analysis (chemistry)