Question

State and explain Beer-Lambert Law.

Answer 1

Beer-Lambert law is a combination of two different laws: Beer’s law and Lambert's law.

Beer’s Law: Beer’s law was stated by August Beer states that concentration and absorbance are directly proportional to each other.

Lambert Law: Johann Heinrich Lambert stated Lambert law. It states that absorbance and path length are directly proportional.

Beer-Lambert Law:

1. According to the Beer-Lambert law, the amount of light that is absorbed by a material that is dissolved in a solvent that completely transmits light is exactly proportional to the substance's concentration and the length of the light's route through the solution.
2. The optical attenuation of a physical substance containing a single attenuating species of uniform concentration is related to the optical path length through the sample and the species' absorptivity in a straightforward and effective way by the Beer-Lambert law.
3. The attenuation of solar or stellar radiation as it passes through the atmosphere is also explained by this formula.
4. The Beer-Lambert law is expressed as: $\mathrm{A}=\mathrm{\epsilon Lc}$

where,

• $\mathrm{A}$ is the amount of light absorbed for a particular wavelength by the sample
• $\mathrm{\epsilon }$ is the molar extinction coefficient
• $\mathrm{L}$ is the distance covered by the light through the solution
• $\mathrm{c}$ is the concentration of the absorbing species

Beer-Lambert formula- $\mathrm{I}={\mathrm{I}}_{\mathrm{o}}{\mathrm{e}}^{-\mathrm{\mu }\left(\mathrm{x}\right)}$

Where,

• $\mathrm{I}$ is the intensity
• ${\mathrm{I}}_{\mathrm{o}}$ is the initial intensity
• $\mathrm{x}$ is the depth in meters
• $\mathrm{\mu }$ is the coefficient of absorption