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concave diffraction grating
concave diffraction grating

concave diffraction grating

Date1908-1912
Inventory Number2029
ClassificationDiffraction Grating
Subject
    Maker American (Johns Hopkins University?)
    Owner Theodore Lyman IV 1874 - 1954
    User Frederick Albert Saunders 1875 - 1963
    User Department of Physics, Harvard University founded 1884
    Cultural Region
      Place of Origin
        Dimensionsdiffraction grating: 6.3 × 6.3 × 1.2 cm (2 1/2 × 2 1/2 × 1/2 in.)
        case: 8.3 × 7.8 × 2.4 cm (3 1/4 × 3 1/16 × 15/16 in.)
        Material
          Accessorieswooden box
          DescriptionConcave diffraction grating made from speculum metal, divided with 31,995 lines per inch and a radius of curvature of 99.3 cm. It is stored in a wooden box (not original).
          Signedunsigned
          Inscribedhandwritten with a pencil: 152-C-3 / 31995 lines / 5.42 cm / Jan 27 1912 / 1908c / JAA / This refers to one meter grating (FAS) in phys 2b.
          Curatorial RemarksThe date suggests that it was made before Saunders arrived at Harvard. It was apparently used for experimental on Balmer lines. Considering the number of gratings found in the CHSI collection coming from the "Rowland factory" at Johns Hopkins University, this one, unsigned, could also have the same provenance.
          FunctionA diffraction grating is a glass or mirror that has regularly spaced microscopic interruptions to the passage of light (lines) such that light passing through or reflected by it experiences interference phenomena, magnifying its magnitude at some angles and cancelling it at others. As this effect depends on the wavelength of light, a diffraction grating is an effective method of decomposing light into its constituent wavelengths, that will be transmitted at different angles (short wavelengths -- bluer -- are deflected less than longer -- redder -- ones). If one knows the line density (lines per inch) and the angle of deflection (with a spectrometer), one can deduce the exact wavelengths.

          Diffraction gratings like this one were often used in astronomy to produce spectra of celestial objects. Begun in 1882, Rowland's gratings were more than an order of magnitude larger and more accurate than any previous one. With these, for instance, it became possible to measure the wavelength of light emitted by atoms to unprecedented accuracy. Rowland himself was able to draw a new and more accurate map of the solar spectrum.

          For more information go to the following website.
          ProvenanceFrom the Department of Physics, Lyman Laboratory, Harvard University.
          concave diffraction grating
          concave diffraction grating
          American
          Date: circa 1925
          Accessories: metal box
          Object number: 2027
          concave diffraction grating
          concave diffraction grating
          American
          Date: circa 1924
          Accessories: wooden box
          Object number: 2025
          Rowland concave diffraction grating
          Rowland concave diffraction grating
          American
          Date: 1903
          Accessories: wooden box
          Object number: 2036
          concave diffraction grating
          concave diffraction grating
          Robert W. Wood
          Date: circa 1925
          Accessories: wooden box
          Object number: 2040
          concave diffraction grating
          concave diffraction grating
          Robert W. Wood
          Date: 1927
          Accessories: aluminum box
          Object number: 2026
          Rowland concave diffraction grating
          Rowland concave diffraction grating
          Henry A. Rowland
          Date: circa 1884
          Accessories: wooden box; key
          Object number: 2031
          concave diffraction grating
          concave diffraction grating
          American
          Date: 1903-1914
          Accessories: box
          Object number: 2038
          concave diffraction grating
          concave diffraction grating
          Adam Hilger Ltd.
          Date: circa 1923
          Accessories: wooden box
          Object number: 2039
          concave diffraction grating
          concave diffraction grating
          American
          Date: 1903
          Object number: 2041
          concave diffraction grating
          concave diffraction grating
          American
          Date: 1910-1940
          Object number: 2042
          concave glass diffraction grating
          concave glass diffraction grating
          Robert W. Wood
          Date: 1928
          Accessories: wooden box
          Object number: 2022
          wood concave diffraction grating
          wood concave diffraction grating
          Robert W. Wood
          Date: 1932
          Accessories: wooden case
          Object number: 2024