Fabry-Perot interferometer
Date: circa 1949
Inventory Number: 1998-1-0470a
Classification: Interferometer
Dimensions:40.7 × 46.7 × 21.2 cm (16 × 18 3/8 × 8 3/8 in.)
Accessories: small box of parts: CENCO filters (2), glass cuvettes (3), brass/glass cuvettes (3), misc. filters, and metal/black enamel cover; instruction manual, catalogue and correspondence in instrument's file
Description:
An apparatus consisting of two half-silvered mirrors placed in front of each other. Both are mounted on a platform such that one is fixed, while the other can move on a worm-drive over a long, graduated track (0-200 mm). The side of the platform with the fixed mirror has two knobs that move the worm-drive, one large in front and one smaller to the side. The movable platform on which the other mirror stands has knobs near the mirror for changing its angle.
The platform can rotate horizontally on a heavy metal base with three leveling screws at its bottom.
Signedon plaque: HILGER / MADE IN ENGLAND
another plaque: JARRELL-ASH COMPANY / SCIENTIFIC INSTRUMENTS / BOSTON 16, MASS.
FunctionA Fabry-Perot interferometer consists of two partially reflecting surfaces placed parallel a close distance from each other. When light enters from one side, it reflects back and forth between the mirrors, with some of the light coming out of the other side at each reflection. Light coming out of the interferometer will be a combination of all the fractions of light from every reflection, all interfering with each other. For a specific wavelengh of light, there will be incidence angles and distances between the mirrors at which the outcoming light will interfere constructively, which will not be the same of other wavelengths. As a result, one of the main uses for these interferometers is to filter unwanted wavelenghts from a light source. These interferometers can also be useful for measuring small distances by observing the change in the interference pattern of the outcoming light as the mirror is moved.
Historical AttributesThe interferometer was bought from its supplier Jarrel-Ash by Bowdoin College in 1951 (see instrument's file in the CHSI library).
ProvenanceFrom the Department of Physics, Bowdoin College.