concave diffraction grating
Datecirca 1915
Inventory Number2032
ClassificationDiffraction Grating
Subject
Attributed to
Bausch & Lomb Optical Company
1853-present
User
Department of Physics, Harvard University
founded 1884
Cultural Region
Place of Origin
Dimensions25.5 × 43.2 × 40.6 cm (10 1/16 × 17 × 16 in.)
Material
DescriptionThe diffraction grating, made of solid speculum metal, is divided with 12,003 lines per inch. Its radius of curvature is unknown. The grating is mounted on a heavy cast iron mount supported by three leveling screws. Precision screws are also used to finely orient the grating.
Signedunsigned
Curatorial RemarksThe mount and the grating probably came together. A note in the instrument's file dated 1965 mentions: "Came from Littrow Mount (long tunnel being used by Klemperer)." Littrow mount means it was originally designed to be used with a Littrow spectrograph. Klemperer is most likely William Klemperer, a professor of physical chemistry at Harvard since the mid 1950s.
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.
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.
Henry A. Rowland
Date: circa 1884
Accessories: wooden box; key
Object number: 2031
Adam Hilger Ltd.
Date: circa 1923
Accessories: wooden box
Object number: 2039
