Optical density

Optical density (OD) is a value that characterizes the absorption of light in a layer of a substance. It is expressed in logarithmic form and is defined as the logarithm of the ratio of the intensity of light passing through a substance to the intensity of light incident on it.

Optical density is one of the most important characteristics of chemical analysis, which is widely used in various fields of science and technology. It is measured in units of the percentage of darkening of the sample after passing a light beam through it and reflects the amount of light absorbed.

In simple terms, optical density (OD) measures how much a beam of light is absorbed by a sample.