Signedon sign on bracket: JARRELL-ASH COMPANY / BOSTON, MASS.
Inscribedon sign on bracket: 3 METER SPECTROGRAPH / JARRELL-ASH COMPANY / BOSTON, MASS. / SERIAL NO. 11
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.
Historical AttributesThis concave diffraction grating (2052a) and its concave mirror (2052b) were both removed from a "large heavy metal spectrograph about 1.25 meters long and one meter wide in triangular form," which were used in the Biophysics Research Laboratory at Peter Bent Brigham Hospital.
ProvenanceRetrieved from the Biophysics Laboratory at the Peter Bent Brigham Hospital, with the help of Dr. Bert L. Vallee, 1976.