What is the equation used to calculate absorbance in a sample?

The equation used to calculate absorbance in a sample is based on the relationship between absorbance (A), transmittance (T), and the logarithmic scale. The correct equation is represented as A = -log(T), where absorbance is defined as the logarithm of the reciprocal of transmittance.

Transmittance refers to the fraction of incident light that passes through a sample. Absorbance measures how much light is absorbed by the sample, and it is directly related to the concentration of the absorbing species and the path length of the light through the sample.

By taking the negative logarithm of transmittance, this equation emphasizes that as more light is absorbed (and therefore less light transmits through), the absorbance value increases. This aligns with Beer's law, which states that absorbance is proportional to concentration and path length. When the transmittance is low (indicating high absorbance), the log term moves towards positive values when negated.

Thus, this equation effectively communicates the inverse relationship between transmittance and absorbance, establishing a clear link between the two concepts in the context of spectrophotometry.