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Creation of interference fringes by an optical flat on a reflective surface. Light rays from a monochromatic source pass through the glass and reflect off both the bottom surface of the flat and the supporting surface. The tiny gap between the surfaces means the two reflected rays have different path lengths.
The interferometric visibility (also known as interference visibility and fringe visibility, or just visibility when in context) is a measure of the contrast of interference in any system subject to wave superposition. Examples include as optics, quantum mechanics, water waves, sound waves, or electrical signals.
How interference fringes are formed by an optical flat resting on a reflective surface. The gap between the surfaces and the wavelength of the light waves are greatly exaggerated. Newton (test plate) interferometry is frequently used in the optical industry for testing the quality of surfaces as they are being shaped and figured.
Yellow areas produce bright lines of constructive interference. The dark areas produce dark lines of destructive interference. In interferometry experiments such as the Michelson–Morley experiment, a fringe shift is the behavior of a pattern of “fringes” when the phase relationship between the component sources change.
If, as in Fig. 3b, M 1 and M' 2 are tilted with respect to each other, the interference fringes will generally take the shape of conic sections (hyperbolas), but if M 1 and M' 2 overlap, the fringes near the axis will be straight, parallel, and equally spaced (fringes of equal thickness). If S is an extended source rather than a point source as ...
The angular spacing of the fringes, θ f, is then given by / where θ f <<1, and λ is the wavelength of the light. It can be seen that the spacing of the fringes depends on the wavelength, the separation of the holes, and the distance between the slits and the observation plane, as noted by Young.
This interference results in a pattern of bright and dark lines or bands called "interference fringes" being observed on the surface. These are similar to contour lines on maps, revealing differences in the thickness of the air gap. The gap between the surfaces is constant along a fringe.
In Young's experiment, the individual slits display a diffraction pattern on top of which is overlaid interference fringes from the two slits (Fig. 2). In contrast, the Lloyd's mirror experiment does not use slits and displays two-source interference without the complications of an overlaid single-slit diffraction pattern.