Experiment: Michelson's Interferometer II

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Description
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Objective: Determine the refractive index of glass

A Michelson interferometer can be used for interferometric measurement of refractive indices in particular because it is sensitive to changes in the optical path of a split beam of light. If the geometric path is kept constant, then refractive indices or changes in refractive index can be determined from the changes in pressure, temperature or density. A slight modification alters the Michelson interferometer into a Twyman-Green interferometer which allows the quality of optical instruments’ surfaces to be measured. In the experiment the refractive index of glass is to be obtained by determining the path differences for light passing through a glass block rotated to various angles as a function of said angles. The path differences are established by counting rings created by constructive or destructive interference. In addition the surface quality of an adhesive strip can be assessed from disruptions in the interference rings which result from the uneven surface of the adhesive tape.