replica transmission grating for use with celestial telescope
Date: 1910-1920
Inventory Number: 2053
Classification: Diffraction Grating
Maker: R. W. Jool ?
User: Oak Ridge Station (1931 - 2005)
User: George R. Agassiz Station, Harvard (1951 - 1982)
User: Harvard College Observatory (founded 1839)
Cultural Region:
Place of Origin:
Dimensions:
12.6 × 17.7 × 1.3 cm (4 15/16 × 6 15/16 × 1/2 in.)
Material:
Description:
This grating is a replica of a diffraction grating. It is made of a plastic film held between two glass plates. The tape holding the plates together is crumbling, and the plastic film is disintegrating.
Signedunsigned
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.
Curatorial RemarksAn information from the old database mentions the following: "1940. 600 to inch R.W. Jool". The origins of this information is unknown.
ProvenanceFrom the Agassiz Station (Oak Ridge Observatory), Harvard University, transferred to CHSI.