2CLabManual201303

Visible light therefore may be used to study colored

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Unformatted text preview: tromagnetic radiation spectrum while reflecting other photons in the visible light region. As a result of the reflected photons, a particular substance appears a certain color. Visible light, therefore, may be used to study colored substances. This is referred to as spectrophotometry. For example, a blade of grass is green, because its chlorophyll absorbs red and blue wavelengths strongly and green less strongly, so most of the green is reflected, as shown by Figure 1 below. The height and shape of the curve make up a characteristic absorption spectrum for a substance and can be used for identification purposes. The curve varies in height because chlorophyll absorbs incoming wavelengths to different extents. The absorption spectra is of chlorophyll a and chlorophyll b is shown below. There is high absorption of red and blue frequency photons, hv. 47 Figure 1. The absorption spectra of chlorophyll a and chlorophyll b. Red Yellow Green Blue A spectrophotometer (or spectrometer, for short) is used to measure absorption spectra and is a combination of a light source that emits a continuous band of radiation, a monochromator (usually...
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