Beer Lambert Law Calculator

What is the Beer Lambert Law?

The Beer Lambert Law (also known as Beer's Law) describes the relationship between the absorbance of a light passes through a solution and the properties of the solution. The law states that the absorbance (A) is directly proportional to the concentration (c) of the absorbing species and the path length (b) of the light through the solution:

A = εbc

Where:

• A = Absorbance (unitless)
• ε = Molar absorptivity or molar extinction coefficient (L·mol⁻¹·cm⁻¹) - a measure of how well a substance absorbs light at a specific wavelength
• b = Path length of the solution (cm) - the distance that light travels through the solution
• c = Concentration of the absorbing species (mol·L⁻¹)

How to Use This Calculator

1. Enter the known values for Wavelength (λ), Molar Absorptivity (ε), Path Length (b), Concentration (c), and Absorbance (A). Make sure to select which value you want to calculate (if any).
2. Click the Calculate button to compute the unknown values.
3. The results will be displayed in the right panel.

Example Usage

Suppose you have a solution with a molar absorptivity (ε) of 4.5 L·mol⁻¹·cm⁻¹ at a wavelength of 450 nm. The light passes through a path length (b) of 1 cm. If you measure an absorbance (A) of 0.35, you can calculate the concentration (c) as follows:

c = A / (εb) = 0.35 / (4.5 × 1) = 0.0778 mol·L⁻¹

This calculator can be used in various applications such as:

• Quantitative analysis in chemistry labs
• Determining the concentration of unknown solutions
• Calibrating spectrophotometers
• Analyzing biological samples