Absorptivity

by Tega Jessa on January 3, 2011

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Absorptivity

Absorption Spectrum by the Hubble Space Telescope


Absorptivity also known as molar absorptivity is the incidence of certain wavelengths of radiation absorbed by a compound. This concept is explained by the Beer-Lambert Law. The law basically states that absorptivity or absorptance is an innate trait of a compound and that it is the function of the compounds density and the length of the path way that light must pass through. Absorptivity is an important characteristic used in chemical analysis namely, through the process of spectroscopy.

Thee basis of absorptivity is the Beer-Lambert law which as mention shows the relationship between the density and concentration of the compound and the distance light passes through it. This gives us a better understanding of how much electromagnetic radiation is absorbed by the material. The Beer-Lambert Law was first developed in 1729 by Pierre Bouguer. However the reason it is called the Beer-Lambert Law is because of two different sets of circumstances. The first was that Bouguer’s work was appropriated by scientist Johann Lambert who quoted Bouguer in his own paper. The Name Beer was attached to the name in 1852 when August Beer extended the low to include the absorption coefficient in the concentration of chemicals in solutions.

The applications of Absorptivity are important to the field of absorption spectrometry. Absorption spectrometry works with the device determining the absorption spectrum of a given substance. In general the absorption spectrum will look like a full visible spectrum with lines of color missing. These lines are the wavelengths of light that are absorbed rather than reflected. This principle has great uses in identifying concentrations of unknown substances in solutions as well as detection of distant objects in space. With the aid of the Beer-Lambert law’s principle of absorptivity scientist are now even able to find planets and determine information like their orbit, rotation, and mass.

We have written many articles about absorptivity for Universe Today. Here’s an article about atomic absorption spectroscopy, and here’s a forum discussion about emissivity and absorptivity.

If you’d like more info on absorptivity, check out this article from Wikipedia. Also, here’s a nice introduction to the Beer-Lambert Law.

We’ve also recorded an entire episode of Astronomy Cast all about Energy Levels and Spectra. Listen here, Episode 139: Energy Levels and Spectra.

Source:
Wikipedia

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