Beer-Lambert Law Calculator

Beer-Lambert law describes the relationship between the absorption of light by a solution and the concentration of the absorbing species. It states that absorbance is directly proportional to the concentration of the solution and the path length of light through the sample.

Absorbance is a dimensionless quantity, meaning it has no units. It's often expressed as AU (absorbance units) for clarity, but mathematically it's just a ratio of light intensities.

Molar absorptivity (extinction coefficient) can be calculated by rearranging Beer's law: ε = A / (c × l), where A is absorbance, c is concentration in molarity, and l is path length in centimeters.

To find concentration from absorbance, rearrange Beer's law: c = A / (ε × l), where c is concentration, A is measured absorbance, ε is the extinction coefficient, and l is the path length.

Transmittance is calculated using the formula: T = 10^(-A), where T is transmittance (as a decimal) and A is absorbance. To express as a percentage, multiply by 100.

Absorbance is affected by three main factors: the concentration of the absorbing species, the path length through the sample, and the molar absorptivity (extinction coefficient) which is specific to each substance and wavelength.

Beer's law may fail at very high concentrations due to molecular interactions, when the solution contains multiple absorbing species, or when the light source is not monochromatic. It's most accurate for dilute solutions with single absorbing species.

Beer-Lambert law is widely used in analytical chemistry for quantitative analysis, including measuring protein concentrations, determining drug concentrations in pharmaceuticals, environmental monitoring, and quality control in various industries.