Interferometer is built by assembling the building blocks on a breadboard as per desired optical layout. Optics and laser head are held using kinematic mounts with two axis fine adjustment facility. Precision alignments for obtaining the interference fringes are done using kinematic mounts.
One of the simplest experiments using the interferometer is measurement of index of refraction of air with an airtight test cell placed in one of the optical arms of the interferometer. No other factor such as convective airflow, should be present, that can generate optical path differences. The flexibility in fringe localization is one of the important advantages of the mach zehnder interferometer over other interferometers. Although many Mach-Zehnder interferometers use a rectangular arrangement, parallelogram arrangements are also possible. Vibration isolated supports for optical table is optional.
The wavelength of laser is calculated by,
λ = ( 2d / N ) Δ
The light passes through a greater length of glass as the plate is rotated. The change in the path length of the light beam as the glass plate is rotated and relates the change in path length with the laser beam through air.
The refractive index of glass slide,
N = ( 2t - Nλ ) ( 1 - cosθ ) / 2t ( 1 - cosθ ) - Nλ
Where t is the thickness of the glass slide, N is the number of fringes counted, λ is the wave length of light used and θ is the angle turned for N fringes.
When a piece of material of thickness d is placed in one arm of the Michelson Interferometer, the change in optical path length is given by 2dn where n is the difference in refractive index between the sample and the material it replaced (usually air). In other words, 2d (nm - nair ) / λ extra wavelengths are introduced if air is replaced by a sample of refractive index nm.
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