Beer Lambert law

Pierre Bouguer was the first to develop the law before 1729. Later, it was attributed to Johann Heinrich Lambert, who cited Bouguer’s findings. Path length was included in the law as a variable that affected absorbance. 

Later, in 1852, Beer expanded the law to include solution concentration, giving the law the name Beer-Lambert Law.

The Beer-Lambert law, also known as Beer’s law, the Lambert-Beer law, or the Beer-Lambert–Bouguer law, relates light attenuation to the properties of the material through which it travels.

What is Beer Lambert law?

When a monochromatic light of initial intensity I0 passes through a solution in a transparent vessel, some of the light is absorbed, resulting in a transmitted light I with a lower intensity than I0.

Some light intensity is lost due to scattering by particles in the solution and reflection at interfaces, but the majority is lost due to absorption by the solution.

The relationship between I and I0 is affected by the absorbing medium’s path length, l, and the concentration of the absorbing solution, c. Lambert and Beer’s laws relate these variables.

Various names for Beer Lambert law

Because more than one law is involved, the Beer-Lambert law is known by many different names.

Pierre Bouguer discovered the law in 1729.

Later, in 1760, Johann Heinrich Lambert cited Bouger’s discovery, stating that a sample’s absorbance is directly proportional to the length of the light path. Despite the fact that Lambert did not claim the discovery, he was frequently credited with it.

August Beer discovered a related law in 1852, stating that absorbance is proportional to sample concentration.

Application of Beer Lambert law

• Electromagnetic spectroscopy makes extensive use of the Beer Lambert law.

Now consider the following Beer Lambert law applications:

• To analyse the drugs, consider the following example of a tablet: Assume we have a tablet and we don’t know which drug is in it. Though we may be familiar with the drug, the question of its molar concentration arises.

• We use electromagnetic radiation (UV rays) to scan the tablet and determine the qualitative (drug present) and quantitative (concentration) properties of the tablet in electromagnetic spectroscopy.

• The same method can be used to calculate bilirubin molar absorbance in blood plasma samples. By measuring the absorbing spectra of various substances in cell structures, we can determine their concentrations.

Importance of Beer’s law:

Beer’s Law is particularly important in chemistry, physics, and meteorology. Beer’s Law is used in chemistry to determine the concentration of chemical solutions, to study oxidation, and to assess polymer degradation. The law also describes how radiation is attenuated as it travels through the Earth’s atmosphere. While the law is normally applied to light, it also aids scientists in understanding the attenuation of particle beams such as neutrons. The Beer-Lambert Law is a theoretical physics solution to the Bhatnagar-Gross-Krook (BKG) operator, which is used in the Boltzmann equation for computational fluid dynamics.

Limitation of Beer’s Lambert law

• Chemical and instrumental factors limit the linearity of the Beer-Lambert law.

The following conditions result in non-linearity of the law:

• The sample’s fluorescence or phosphorescence
• Changes in refractive index when the analyte concentration is high
• Chemical equilibria shifts as a function of concentration
• Deviations in non-monochromatic radiation can be reduced by using a relatively flat part of the absorption spectrum, such as the maximum of an absorption band.
• stray lighting

How Do We Calculate Beer Lambert Law?

The Beer Lambert law can be measured by calculating the concentration of a solution using absorbances. 

Another method is to plot a graph of different concentrations and then align them based on their appropriate or correct absorbencies. The concentration of an unknown solution must then be calculated using a colorimeter.

A spectrophotometer is a device that can measure the intensity, energy carried or handled by the radiation per unit area per unit time, of light that enters and exits a sample solution. 

Furthermore, the two intensities can be expressed as transmittance. Moreover, transmittance is defined as the ratio of the intensity of the exiting light to the intensity of the entering light, expressed as a percentage ( percent T).

Light of different wavelengths would not be absorbed by the same substance. As a result, the wavelength of maximum absorption by the substance is one of the material’s distinguishing properties.

It = I0 for a completely transparent substance, and 100 for its transmittance. Similarly, a substance through which no radiation of a specific wavelength can pass must have It = 0 and a transmittance of 0%.

Conclusion

The Beer-Lambert law, also known as Beer’s law relates light attenuation to the properties of the material through which it travels. Because more than one law is involved, the Beer-Lambert law is known by many different names. Electromagnetic spectroscopy makes extensive use of the Beer Lambert law. Beer’s Law is particularly important in chemistry, physics, and meteorology. The Beer-Lambert Law is a theoretical physics solution to the Bhatnagar-Gross-Krook operator, which is used in the Boltzmann equation for computational fluid dynamics. According to the Beer-Lambert law, there is a linear relationship between solution concentration and absorbance, allowing the concentration of a solution to be calculated by measuring its absorbance.