Spectrophotometric Terms and Beer Lambert Law

A collection of flashcards covering key vocabulary and definitions related to spectrophotometric terms and the Beer Lambert Law.

Transmittance

The ratio of the intensity of transmitted light to the intensity of incident light.

Absorbance

The logarithm of the ratio of intensity of incident light to the intensity of transmitted light.

Beer Lambert Law

A relationship between the attenuation of light through a substance and properties of that substance, formulated as A = ε * c * l.

Molar Absorption Coefficient

A constant for a particular compound at a given wavelength, defined as the absorbance at a concentration of 1mol/L and a path length of 1cm.

Path Length (l)

The length that light has to travel through the solution, measured in centimeters.

Relation between Absorbance and Concentration

According to Beer's Law, absorbance (A) is directly proportional to the concentration (c) of the solution.

Equation for Transmittance

T = I / I0, where T is transmittance, I is transmitted intensity, and I0 is incident intensity.

Equation for Absorbance

A = log(I0 / I), where A is absorbance, I0 is incident intensity, and I is transmitted intensity.

Lambda Max

The wavelength at which a substance exhibits maximum absorbance in a spectrophotometric analysis.

Beer Lambert’s Law is Valid when?

• Concentration is not too high (typically < 0.01 M)

• Monochromatic (single wavelength) light is used

• Solution is homogeneous

• No chemical reactions occur

• No scattering from particles