Spectroscopy can be thought of as working with rainbows, i.e., the separation
of white light into its component colors, which range from red to violet. Seeing a rainbow, or even better, double rainbows, has great aesthetic value but is also part of the science behind analyzing light. On the beauty side, cut glass crystals such as those that might be used in a chandelier will also show the colors of the rainbow. Refining the shape of these crystals for use in science has led to new insight in many fields.
The light intensity as a function of wavelength is known as a spectrum and is used in many analytical systems to determine the composition of materials. It is well known that the sun produces a wide range of wavelengths and that the water vapor in the Earth’s atmosphere blocks many wavelengths from reaching the surface. The areas of the spectrum that can penetrate the atmosphere are known as atmospheric windows. Metallurgy has benefitted from the use of spectrometers for determining temperatures of highly heated metals to ensure that the metal processing happens at the right temperatures.
Optical spectrometers can be made using prisms, which rely on refraction and gratings. Gratings use diffraction to separate out the various wavelengths. Hybrid devices known as grisms are made from combinations of gratings and prisms and have the advantage of making very compact instruments.
In this chapter we will model the some of the key equations used in spectrometers and how they relate to the final spectrum.
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