1. What is the Beer-Lambert Law?

The Beer-Lambert Law relates the attenuation of light to the properties of the material through which the light is traveling. It connects absorbance (A) to transmittance (T) and also to the molar absorptivity (ε), concentration (c), and path length (l) of the absorbing species.

2. How Does the Calculator Work?

The calculator uses two forms of the Beer-Lambert law:

Where:

• \( A \) — Absorbance (unitless)
• \( T \) — Transmittance (0 to 1)
• \( \epsilon \) — Molar absorptivity (L/mol·cm)
• \( c \) — Concentration (mol/L)
• \( l \) — Path length (cm)

Explanation: The law shows that absorbance is directly proportional to concentration and path length when using monochromatic light.

3. Importance of Absorbance Measurement

Details: Absorbance measurements are fundamental in spectrophotometry and are widely used in chemistry, physics, and biology for quantitative analysis of substances.

4. Using the Calculator

Tips: You can calculate absorbance either from transmittance values (0-1) or by providing molar absorptivity, concentration, and path length. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical absorbance values?
A: For accurate measurements, absorbance should typically be between 0.1 and 1. Values above 1 may indicate too concentrated samples.

Q2: What is the relationship between %T and A?
A: %T = T × 100. A = 2 - log10(%T). For example, 10%T = 1.0 A.

Q3: When does the Beer-Lambert law fail?
A: At high concentrations (>0.01M), with polychromatic light, or when there are chemical associations/dissociations.

Q4: What are typical ε values?
A: Typically range from 0 to 10^5 L/mol·cm. Large ε values indicate strong absorption.

Q5: Can I use this for mixtures?
A: For mixtures, the total absorbance is the sum of individual absorbances at a given wavelength.