The Beer-Lambert Law describes a fundamental relationship in analytical chemistry, illustrating how the concentration of a solution affects its ability to absorb light. This law is expressed mathematically as:

A = εlc

In this equation, A represents the absorbance of the solution, ε is the molar absorptivity (a constant that indicates how strongly a substance absorbs light at a particular wavelength), l is the path length of the light through the solution (typically measured in centimeters), and c is the concentration of the solution (measured in moles per liter).

When light passes through a solution, the intensity of the light before entering the solution is denoted as I₀, while the intensity after passing through the solution is I. According to the Beer-Lambert Law, the relationship between these intensities can be expressed as:

A = log₁₀(I₀/I)

This indicates that as the concentration of the solution increases, the absorbance A also increases, leading to a decrease in the transmitted light intensity I. Consequently, a more concentrated solution will absorb more light, resulting in a lower value of I compared to I₀.

Graphically, this relationship can be represented with absorbance plotted on the y-axis and concentration on the x-axis, typically resulting in a linear graph. The peak of this graph, known as the lambda max, indicates the wavelength at which the solution absorbs the most light. Understanding this relationship is crucial for accurately determining the concentration of unknown solutions through spectrophotometric methods.

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