Beer-Lambert's Law describes the relationship between absorbance and which quantities?

• A. Path Length and Wavelength
• B. Molar Absorptivity and Wavelength
• C. Concentration and Path Length
• D. Absorbance and Concentration

Answer: (D)

Beer-Lambert Law shows that absorbance is determined by two main factors of the sample as light passes through it: how much absorbing material is present (concentration) and how far the light travels through the sample (path length). The law is A = ε c l, where A is absorbance, ε is molar absorptivity (which depends on the substance and the wavelength), c is concentration, and l is path length. For a fixed wavelength, and with ε constant, absorbance increases linearly with both concentration and path length. So the quantities directly related to absorbance are concentration and path length.