Optical Benches

  The optical bench is commonly used in physics labs today, and consists of a long, rigid member with a linear scale applied to it. Holders for light sources, lenses and screens are placed on the apparatus so that image formation can be observed. A typical nineteenth century optical bench is shown below. This was made by the Geneva Society for the Construction of Instruments of Physics and was in the collection of Bowdoin College in Brunswick, Maine when I photographed it in 1979.

   The Societe Genevoise optical bench at the left is a later version of the single-rail model above, and is in the Greenslade Collection.

An example of a non-commercial optical bench, built by Prof. Joseph Naylor of Depauw University in Greencastle, Indiana about 1900, is shown below.


   At the right is a surviving slider from a nineteenth century optical bench in the apparatus collection at Colby College in Waterville, Maine. It has an iris diaphragm that may be opened and closed using the small handles. The shelf to the rear was probably used to hold a light source, and the large wooden screen was used to keep extra light from travelling forward.

   A parallel, and perhaps earlier use, of what we now call an optical bench was for the study of thermal radiation. The Italian physicist, Macedonio Melloni (1798-1854), spent his scientific career studying the similarities between light and thermal radiation. The optical bench below, in the Garland Collection of Classic Physics Apparatus at Vanderbilt University, shows some of the typical apparatus used for this work. This often included a source, Locatelli's Lamp, shown on another page. In the middle is a series of stops, mounted on a rotating plate, and resembling the Waterhouse stops used in early cameras (and some Polaroid cameras from the 1950s). The rotating arm and goniometer can be used to hold detectors for radiation refracted by suitable prisms. The differential thermoelectric pile invented by Nobeli was often used as a detector of radiation. On top of the source at the left (the height control for the wick can be seen projecting to the right) is Leslie's cube, used in studies of the rate of emission of various surfaces held at the same temperature.

The apparatus above is unmarked, but the "mahogany board with wooden measuring scale" shown below cost 40 marks in the 1900 Max Kohl apparatus catalogue. This apparatus is in the collection at the College of Wooster in Ohio.

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