What happens to absorbance (A) as transmittance (T) decreases?

To understand the relationship between absorbance (A) and transmittance (T), it's important to recall the definitions and their mathematical relationship. Absorbance is a measure of the amount of light absorbed by a sample, while transmittance refers to the fraction of light that passes through the sample.

The relationship between absorbance and transmittance is given by the equation:

[ A = -\log(T) ]

This equation indicates that as transmittance decreases, which means that less light is passing through the sample, the value of the logarithm becomes larger in magnitude, resulting in an increase in absorbance. In simpler terms, if more light is absorbed (as fewer photons transmit through), the absorbance value will increase.

Thus, when transmittance decreases, absorbance consequently increases because less light is transmitted through the sample due to more absorption. This direct relationship is a cornerstone in spectrophotometry and is fundamental when analyzing how substances interact with light.