The Wadsworth Spectrometer

FIGURE 4-16. Schematic diagram of a Wadsworth mounting for a concave 

FIGURE 4-17. Photograph of a Wadsworth-mounted 1.5-m spectrometer. [Courtesy Jarrell-Ash Division, Fisher Scientific Co.] 

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The Wadsworth spectrometer, shown schematically in Figure 4-16, does not make use of the Rowland circle the focal distance is one-half the radius of curvature and another optical element, a concave collimating mirror, is introduced into the optical path. In this arrangement the photographic plate is mounted on a line normal to the concave grating, and thus stigmatic spectra are produced and the dispersion is linear. 

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