The Beer-Lambert law relates the attenuation of light to the material’s properties through which the light travels. Beer-Lambert law is applied to chemical analysis measurements. Let us familiarise ourselves with the law by reading the article.
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What is the Beer-Lambert Law?
Beer’s law states the following:
For a given material, the sample path length and concentration of the sample are directly proportional to the absorbance of the light.
Various Names for Beer-Lambert Law
The Beer-Lambert law, known by various names such as the Lambert-Beer law, Beer-Lambert–Bouguer law or the Beer’s law. The Beer-Lambert law is known by so many names because more than one law is involved.
- In 1729, Pierre Bouguer discovered the law.
- Later, in 1760, Johann Heinrich Lambert quoted Bouger’s discovery saying that the absorbance of a sample is directly proportional to the path length of light. Although Lambert dint claim the discovery, he was often credited with it.
- In 1852, August Beer discovered a related law which stated that the absorbance is proportional to the concentration of the sample.
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What is Beer’s Law?
Beer law states that concentration and absorbance are directly proportional to each other and it was stated by August Beer. What is Lambert Law? Lambert law states that absorbance and path length are directly proportional and it was stated by Johann Heinrich Lambert. |
Beer-Lambert Law Equation
The Beer-Lambert law equation is as follows:
\(\begin{array}{l}\large I=I_{0}e^{-\mu (x)}\end{array} \) |
Where,
I is the intensity
I0 is the initial intensity
μ is the coefficient of absorption
x is the depth in metre
Learn how to derive the Beer-Lambert Law equation by visiting the page below:
Beer-Lambert Law Applications
This law finds applications in various fields such as:
Analytical chemistry
This analysis mainly concentrates on the separation, quantification, and identification of matter by spectrophotometry. There is no involvement of extensive pre-processing of the sample to get the results. For example, bilirubin count in a blood sample can be determined by using a spectrophotometer.
In atmosphere
Solar or stellar radiation in the atmosphere can be described using this law. The law in atmospheric applications has a modified equation:
Where,
a is the aerosols
g is the mixed gases
RS is the Raman scattering effect.
NO2 is Nitrogen dioxide
w is the water vapour absorption
O3 is Ozone
r is Rayleigh scattering
Beer-Lambert Law Limitations
Using this law it becomes easy to study the absorptivity coefficient of the sample when the concentration is low i.e. <10mM but as the concentration becomes high i.e. >10mM there is a deviation as the electrostatic interactions become more.
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Frequently Asked Questions – FAQs
Who discovered the Beer-Lambert law?
What does the Beer’s Law state?
What is the Beer-Lambert law equation used for?
Why is Beer-Lambert law important?
When does the Beer-Lambert law fail?
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