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Unformatted text preview: a reflection grating with associated optics) to select a narrow
range of wavelengths, and a photoelectric detector to measure the light intensity, as
indicated in Figure 2.
Source |ℓ |
Sample Figure 2: Schematic Representation of a Spectrophotometer.
In addition to identifying a substance, an absorption spectrum can be used to determine
its concentration because the absorbance, the amount of light of a given wavelength
absorbed by a substance, is proportional to the number of molecules present in the
sample. This relationship is called the Beer-Lambert Law or more simply Beer’s Law.
Consider monochromatic light of a given intensity incident on a sample, as shown in
Figure 2. If this light can be absorbed by the sample, then the transmitted light will have
a lower intensity than the incident light. The transmittance, T, is defined as the ratio of
the transmitted intensity, I, to the incident intensity, I0,
I0 The percent, %T, is simply 100 T. The transmittance is decreased if either the
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This note was uploaded on 04/09/2013 for the course CHE CHE 2C taught by Professor Nasiri during the Spring '07 term at UC Davis.
- Spring '07