flat diffraction grating mounted in stand
Datecirca 1878
Inventory Number2028
ClassificationDiffraction Grating
Subject
Maker
Daniel C. Chapman
1826 - 1894
Maker
Lewis M. Rutherfurd
1816 - 1892
Owner
Theodore Lyman IV
1874 - 1954
User
Department of Physics, Harvard University
founded 1884
Cultural Region
Place of Origin
Dimensions9.6 × 13.1 × 6.6 cm (3 3/4 × 5 3/16 × 2 5/8 in.)
Material
DescriptionFlat diffraction grating made from speculum metal, divided with 17,296 lines per inch. (Because it is flat, it has obvioulsy no radius of curvature.) It is mounted in a brass stand (held by string windings) supported by three leveling screws. The leatherette case in which is was stored was deaccessioned owing to his poor condition.
Signedon bottom, etched: Manf by D.C. Chapman / with L.M. Rutherfurd's Engine
Inscribedon top, etched: May 23, 1878. 33120 Spaces 17296 per inch
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. Robert Wood was trained by Rowland at Johns Hopkins University when the former was appointed professor of physics there.
For more information go to the following website.
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. Robert Wood was trained by Rowland at Johns Hopkins University when the former was appointed professor of physics there.
For more information go to the following website.
ProvenanceFrom the Department of Physics, Lyman Laboratory, Harvard University.
Daniel C. Chapman
Date: 1877
Accessories: wooden box
Object number: 2047
Lewis M. Rutherfurd
Date: 1877
Accessories: leather case
Object number: 2044
Henry A. Rowland
Date: circa 1884
Accessories: wooden box; key
Object number: 2031
