Filters, Prisms, Gratings, and Lenses

FILTERS, PRISMS, GRATINGS, AND LENSES 4.6. Holographic Gratings... 

To use atomic spectra for analytical purposes, regardless of the application, certain basic instrumentation is required. Included are a spectral isolation device—filter, prism, or grating a slit to permit the radiation to strike the monochromator as a narrow beam a device to allow observation of the spectrum and the necessary optics, lenses, mirrors, etc. to collect and focus the incident light beam. These devices, assembled into one instrument, constitute the monochromator. Some lenses and mirrors, an optical bench, and the instrumentation for observing the spectrum are or may be external to the basic monochromator. 

A monochromator consists chiefly of lenses or mirrors to focus the radiation, entrance and exit slits to restrict unwanted radiation and help control the spectral purity of the radiation emitted from the monochromator, and a dispersing medium to separate the wavelengths of the polychromatic radiation from the source. There are two basic types of dispersing elements, the prism and the difrfaction grating. Various types of optical filters may also be used to select specific wavelengths. 

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