Wavelength, light, measurement technique

In spectroscopic investigations, the intensity transmitted or reflected by the sample is compared with the intensity of the incident light at a given wavelength or frequency thus, with a spectrometer, intensities and wavelengths are measured simultaneously. Intensities are determined by means of an infrared detector. Clearly, the performance of the detector is just as important to the spectroscopist, as that of the source, but these and other problems of infrared technique are beyond the scope of this introduction and the reader is referred to the literature 3.3). 

Notice in the photo the colorful compoimds of transition metals. When placed in solutions, these compounds absorb different wavelengths of light. Visible spectroscopy uses light absorption at specific wavelengths to measure the concentration of colored compounds in solution. This method of analysis uses the interaction of valence electrons of transition elements and visible light. Because many transition element compounds are colored, this technique can be used in transition element analysis. 

Although the SPV method has been in use since 1961 it has not found wide acceptance. One reason for this is the tedious and slow nature of the measurement technique. The wavelength for the appropriate a and the light intensity for the constant Vgpy had to be adjusted manually in earlier systems. These adjustments are made by a computer in more recent systems. Another reason for its limited use is that, as of 1987, there was no commercial instrument available. 

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