Question

state beer lambert law

Answer 1

The Beer-Lambert law (also called the Beer-Lambert-Bouguer law or simply Beer's law) is the linear relationship between absorbance and concentration of an absorber of electromagnetic radiation. The general Beer-Lambert law is usually written as:

$$\mathrm {A} = \mathrm {a} _ {\lambda} \times \mathrm {b} \times \mathrm {c}$$

where A is the measured absorbance, aλ is a wavelength-dependent absorptivity coefficient, b is the path length, and c is the analyte concentration. When working in concentration units of molarity, the Beer-Lambert law is written as:

$$\mathrm {A} = \varepsilon_ {\lambda} \times \mathrm {b} \times \mathrm {c}$$

where ελ is the wavelength-dependent molar absorptivity coefficient with units of M⁻¹ cm⁻¹. The λsubscript is often dropped with the understanding that a value for ε is for a specific wavelength. If multiple species that absorb light at a given wavelength are present in a sample, the total absorbance at that wavelength is the sum due to all absorbers:

$$\mathrm {A} = \left(\varepsilon_ {1} \times \mathrm {b} \times \mathrm {c} _ {1}\right) + \left(\varepsilon_ {2} \times \mathrm {b} \times \mathrm {c} _ {2}\right) + \dots$$

where the subscripts refer to the molar absorptivity and concentration of the different absorbing species that are present.