concave diffraction grating for 3-meter spectrograph

Datecirca 1946

Inventory Number2052a

ClassificationDiffraction Grating

Subject

Maker Jarrell-Ash Company 1933 - 1968

User Biophysics Research Laboratory, Peter Bent Brigham Hospital founded 1954

Cultural Region

Place of Origin

Dimensions15 × 13.4 × 10 cm (5 7/8 × 5 1/4 × 3 15/16 in.)

Material

DescriptionThis concave diffraction grating went to a 3-meter spectrograph. The concave diffraction grating consists of a glass disk (11.5 cm in diameter) with a silvered inner surface upon which the rulings were made. The grating is housed in cast aluminum collar with a black crackle finish. This collar is attached to an iron, angle bracket. One can see through to the back of the grating.

With the concave grating, there is a concave mirror in a cast aluminum housing. It has a rectangular, flap door. (see 2052b)

Signedon sign on bracket: JARRELL-ASH COMPANY / BOSTON, MASS.

Inscribedon sign on bracket: 3 METER SPECTROGRAPH / JARRELL-ASH COMPANY / BOSTON, MASS. / SERIAL NO. 11

Curatorial RemarksOther parts to the spectrograph were missing or in very poor shape, and were not brought to CHSI.

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.

ProvenanceRetrieved from the Biophysics Laboratory at the Peter Bent Brigham Hospital, with the help of Dr. Bert L. Vallee, 1976.

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.