Beer Lambert Law Calculator

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If the solution absorbs light, the intensity of the light emerging from the container will be less than Io\text I_\text o. If the intensity of the transmitted light is I\text I, we can define the absorbance A\text A as:

A=log⁡10(Io/I)\text A = \log_{10} (\text I_\text o / \text I)

We can express Beer's law equation as:

A=log⁡10(Io/I)=ε×l×c\text A = \log_{10} (\text I_\text o / \text I) = \varepsilon \times \text l \times \text c

where:

  • ε\varepsilon -Molar absorption coefficient or the molar absorptivity;
  • l\text l -Path length of the beam in the sample; and
  • c\text c -Concentration of the solution.

In spectroscopy, the path length is usually expressed in cm, and absorbance is unitless (a dimensionless quantity). The unit for expressing the concentration of sample solution is mol/L, and hence the units of molar absorptivity are L/mol·cm.

Might we recommend trying out our molarity calculator? It helps convert the mass concentration of any solution to a molar concentration.

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