Beer-Lambert Law Calculator
Calculate absorbance, concentration, and transmittance using Beer-Lambert law
Calculate Using Beer-Lambert Law
Molar extinction coefficient (characteristic of the substance)
Molar concentration of the solution
Thickness of the sample through which light passes
Beer-Lambert Law Results
Beer-Lambert equation: A = εlc = log₁₀(I₀/I)
Transmittance relation: T = I/I₀ = 10⁻ᴬ
Calculation: A = 0 × 0.00 × 0.000000 = 0.0000
Spectroscopic Analysis
Example Calculation
Sample Problem
Substance: Protein solution
Molar absorptivity (ε): 8,400 L/mol·cm
Concentration (c): 4.33×10⁻⁵ mol/L
Path length (l): 1 cm
Solution
A = εlc
A = 8,400 × 1 × 4.33×10⁻⁵
A = 0.364 AU
T = 43.3%
Beer-Lambert Components
Absorbance
Dimensionless quantity
A = log₁₀(I₀/I)
Molar Absorptivity
L/mol·cm
Substance-specific constant
Path Length
Usually in cm
Sample thickness
Concentration
mol/L
Molar concentration
Applications
Analytical Chemistry
Quantitative analysis
Concentration determination
Biochemistry
Protein quantification
Enzyme kinetics
Environmental
Water quality testing
Pollutant monitoring
Pharmaceuticals
Drug analysis
Quality control
Spectroscopy Tips
Optimal absorbance range: 0.1-1.0 AU
Law assumes monochromatic light
Dilute solutions for linearity
Use appropriate blank/reference
Understanding Beer-Lambert Law
What is Beer-Lambert Law?
The Beer-Lambert law describes the relationship between the absorbance of light by a solution and the concentration of the absorbing species. It states that absorbance is directly proportional to the concentration of the solution and the path length through which light travels.
Key Principles
- •Light intensity decreases exponentially with concentration
- •Relationship is linear for dilute solutions
- •Assumes monochromatic light and no scattering
- •Forms basis of quantitative spectroscopy
Mathematical Relations
Beer-Lambert Equation
A = εlc
Linear relationship with concentration
Absorbance Definition
A = log₁₀(I₀/I)
Logarithmic relationship with intensities
Transmittance
T = I/I₀ = 10⁻ᴬ
Fraction of light transmitted
Note: The law assumes no molecular interactions, scattering, or fluorescence. Deviations occur at high concentrations or with complex samples.