Prism, spectral analysis

This layer is then analysed directly by internal reflectance infra-red spectroscopy. Since there is no handling of the sample, contamination is reduced to a minimum. However, only infra-red spectral analysis is possible with this system since the material absorbed on the germanium prism is always a mixture of compounds, and since the spectrophotometer used for the production of the spectra is not a high-precision unit, the information coming from this technique is limited. While identification of specific compounds is not usually possible, changes in spectra, which can be related to the time of day, season, or to singular events, can be observed. 

The Fraunhofer s spectroscope was constructed to receive light that had been passed through a slit and a tube to create a narrow beam, resulting in a spectrum beyond the prism that was then viewed through a telescope. This instrument allowed Fraunhofer to construct for the first time a map of the dark line spectra from the Sun, the principal lines from which he named with the letters A through G—the now-familiar Fraunhofer lines. In 1814—1815, he published his Sun and stellar studies that gave spectral analysis a real boost. 

Now we will see that sine waves are extremely important for yet one more reason. We ll learn that just as light can be passed through a prism to break it into the individual light frequencies from which it is composed, sound can be separated into individual simple frequencies (sine waves). The set of individual amplitudes and phases of the sines that make up a sound are called a frequency spectrum. The mathematical technique used to turn a time-domain waveform into a frequency-domain spectrum is called a transform. The math used to turn a frequency-domain spectrum back into a time-domain waveform is called an inverse transform. Using the frequency spectrum to inspect aspects of a sound is called spectral analysis. 

Atomic spectroscopy is the oldest instrumental elemental analysis principle, the origins of which go back to the work of Bunsen and Kirchhoff in the mid-19th century [1], Their work showed how the optical radiation emitted from flames is characteristic of the elements present in the flame gases or introduced into the burning flame by various means. It had also already been observed that the intensities of the element-specific features in the spectra, namely the atomic spectral lines, changed with the amount of elemental species present. Thus the basis for both qualitative and quantitative analysis with atomic emission spectrometry was discovered. These discoveries were made possible by the availability of dispersing media such as prisms, which allowed the radiation to be spectrally resolved and the line spectra of the elements to be produced. 

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