concave diffraction grating
Date: circa 1923
Inventory Number: 2039
Classification: Diffraction Grating
Subject:
Maker: Adam Hilger Ltd. (1874 - 1948)
Owner: Theodore Lyman IV (1874 - 1954)
User: Department of Physics, Harvard University (founded 1884)
Cultural Region:
Place of Origin:
Dimensions:
7.2 × 7.2 × 1.2 cm (2 13/16 × 2 13/16 × 1/2 in.)
box: 9.2 × 8.9 × 2.8 cm (3 5/8 × 3 1/2 × 1 1/8 in.)
Material:
Accessories: wooden box
Description:
Circular diffraction grating, made of speculum metal, with unknown lines per inch. The radius of curvature is 50 cm. It is stored in box.
Signedfound on card: No. 51653 New [underlined] Ruled / on Blythswood engine Dec. 1923 / from Hilger
Inscribedon back plate: 1/2 M 51653
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.