Absorbance
Absorbance
Absorbance (pronounced: /əbˈsɔːrbəns/), also known as optical density, is a measure of the quantity of light absorbed by a substance. It is a key concept in the fields of spectroscopy and photochemistry.
Etymology
The term "absorbance" is derived from the English word "absorb", which originates from the Latin "absorbēre", meaning "to swallow up". This is a reference to the way in which substances absorb light.
Definition
Absorbance is defined as the logarithm of the ratio of incident to transmitted radiant power through a material, and it is dimensionless. The mathematical formula for absorbance is:
A = log10 (I0 / I)
where:
- A is the absorbance
- I0 is the intensity of the incident light
- I is the intensity of the transmitted light
Related Terms
- Transmittance: The ratio of the intensity of the light that has passed through the sample to the intensity of the light when it enters the sample.
- Reflectance: The fraction of incident light that is reflected by a surface.
- Spectrophotometry: A method used to measure the absorbance of light by a chemical substance.
- Beer-Lambert Law: A linear relationship between absorbance and concentration of an absorbing species.
Applications
Absorbance is a fundamental concept in various scientific fields such as chemistry, biology, physics, and environmental science. It is commonly used in procedures such as DNA sequencing, protein assay, and water quality testing.
External links
- Medical encyclopedia article on Absorbance
- Wikipedia's article - Absorbance
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