log10transmittance

Log10transmittance refers to the logarithm base 10 of the transmittance of a material or system, commonly written as log10(T). Transmittance T is the fraction of incident light that passes through a sample, typically ranging from 0 to 1 (or 0% to 100%). The quantity log10(T) is unitless and is always less than or equal to zero, being zero only when the sample transmits all light (T = 1). As transmittance decreases toward zero, log10(T) becomes increasingly negative.

Mathematically, log10transmittance is related to absorbance A by A = -log10(T). Therefore log10(T) = -A. This relationship means that a higher absorbance corresponds to a more negative log10transmittance. Absorbance is widely used in spectroscopy because it, along with the Beer-Lambert law, often correlates linearly with concentration.

When transmittance is given as a percentage, it must first be converted to a fraction by dividing by 100 before taking the base-10 logarithm. For example, T = 0.8 yields log10(T) ≈ -0.0969, and T = 0.01 yields log10(T) = -2.

Applications and terminology: decadic transmittance is a term sometimes used to describe log10(T). The phrase log10transmittance emphasizes the logarithmic scale of transmittance, but in many contexts absorbance is preferred for reporting data. It is important to specify whether a logarithmic transformation has been applied to avoid misinterpretation.