Wadsworth constant deviation system


In optics, Wadsworth's constant-deviation prism-mirror system (or Wadsworth constant deviation mounting) is a method to arrange a prism or diffraction grating and a mirror on a turntable to ensure that rays of light emerge in a fixed direction.[1] Typically, light entering via a slit is directed into the prism by a lens. A particular wavelength can be chosen for analysis by setting the angle of the prism, and hence the part of the spectrum that exits by a mirror and lens combination. Rotating the prism through its entire range of motion enables the entire spectrum to be analyzed.[2]

An analytical proof for the arrangement was given by Wadsworth,[1] followed almost three decades later with a geometric proof by Gibbs and Collins.[3] It is considered a "classic" prism configuration being versatile on its own or in combination with many other configuration and instrumentation combinations.[4]

Among many other applications, Wadsworth constant deviation mountings have been used to study light emissions from excited metal atoms,[5] and to study the light needs of plants in future space missions.[2]


  1. ^ a b Wadsworth, Frank L. O. (1894). "The Modern Spectroscope. IX. Fixed-Arm Spectroscopes". Astronomy and Astro-Physics. 13: 835. OL 23382270M.
  2. ^ a b Alnwick, Leslie; Clark, Amy; Debs, Patricia; Franczek, Chris; Good, Tom; Rodrigues, Pedro (1 December 1989). "Design and implementation of sensor systems for control of a closed-loop life support system". NASA-CR-186675. Retrieved 5 July 2015. Cite journal requires |journal= (help)
  3. ^ Gibbs, R. C.; Collins, J.R. (1922). "Geometrical Proof for the Wadsworth Constant Deviation System" (PDF). Physical Review. 19: 381. doi:10.1103/physrev.19.381.
  4. ^ George J . Zissis (1995). "Dispersive prisms and gratings" (pdf) in Michael Bass et al. (eds.) Handbook of Optics. Vol. 2, Ch. 5. McGraw Hill.
  5. ^ Lund, H.; Ward, L. (1952). "The Spectral Emissivities of Iron, Nickel and Cobalt". Proceedings of the Physical Society, Section B. 65 (7): 535–540. Bibcode:1952PPSB...65..535L.