posted by kim on .
using a spectrophotometer what is the relationship between absorbance and the concentration of light absoring substance in a solution.
Absorbance is a term used by chemists. It is the log to base 10 of Io/I. where Io is the intensity of light (or infrare radiation) entering a sample and I is what comes out at a specific wavcelength. It is related to path length (cm), species concentation (moles/lieter) and a species-dependent absorption parameter in liters*mole^-1*cm^-1
As a physicist, I was taught to use the term absorptance, which is somewhat different, I/Io. If the absorptance is A for a light beam travelling through a sample of path length L,
A = 1 - e^(-kL), where
k is the absorption coefficient. k is what is proportional to the concentration of the light-absorbing substance.
In spectroscopy, the absorbance A is defined as
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