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BEER LAW [1 record]

Record 1 1989-02-28

English

Subject field(s)
  • Analytical Chemistry
  • Optics
DEF

a law in physics: the absorption of light by different concentrations of the same solute dissolved in the same solvent is an exponential function of the concentration provided the thickness of the absorbing medium remains constant.

CONT

The law discovered by Beer in 1852, that the absorption coefficient for light passing through a solution of a given salt in a non-absorbing solvent is proportional to the concentration. ...Sometimes written I = I0e- a[alphacx where I is the intensity of light transmitted, I4 is the intensity of the incident light, e is the natural logarithmic base, c is the concentration of the solution in moles per liter, x is the thickness of the transmitting layer, and a [alpha] is the molar absorption coefficient.

OBS

In general, Beer's law is used for light of a particular narrow wavelength band and then "a" [alpha] is the specular molar absorption coefficient. The Beer law is also written I = I010ecx where "e" is known as the molar extinction coefficient. Not all solutions obey the Beer law.

OBS

See also the "Bouguer law".

French

Domaine(s)
  • Chimie analytique
  • Optique
DEF

loi qui permet de calculer la quantité de lumière transmise à travers une épaisseur donnée x de substance absorbante. Elle s'exprime par la relation I = I0e-ax, I étant l'intensité transmise, I0 l'intensité initiale et "a" [alpha] une constante.

DEF

Loi limite, à la base de la colorimétrie, indiquant qu'aux faibles concentrations et pour une longueur d'onde déterminée, l'intensité I de la lumière transmise est donnée par I = I0. e-kcl en appelant I0 l'intensité initiale, "c" la concentration de la substance dissoute et "l" l'épaisseur traversée.

Spanish

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