Biology 2290F/G Study Guide - Final Guide: Radiant Flux, Dichlorophenolindophenol, Diffraction Grating
17 Apr 2016
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Radiant energy from wavelengths 340 to 900nm is supplied by a tungsten lamp. Diffracting gradient, like a glass prism splits the light into its component wavelength. Different wavelengths are selected by changing the positioning of the diffraction grating so that light of a very narrow range of wavelength passes through a split before it reaches the sample. Any light transmitted (not absorbed) by the sample reaches a phototube that transduces the light energy to an electric current. Note: the spectrophotometer does not measure absorbance even though it gives information on both. Measure the amount of light transmitted by the sample. This transmittance is then compared with the transmittance of a reference blank to determine how much light has been absorbed. Light interacts with matter in a number of ways: absorbed, transmitted, or reflected. If a substance appears colored when illuminated with white light the colour we see corresponds to the wavelength most transmittance or reflected by that substance.
