New Localized Interference Fringes

Abstract

IN this note a description is given of a simple method for producing a new type of sharp localized interference fringes with interesting properties. These sharp fringes are best formed by multiple-beam interference, although a broadened variant can be obtained with two beams. They arise when a plane parallel sheet of flexible material silvered on both sides is bent into a curve (suitable radii of curvature are 1–5 cm.) and illuminated with strictly parallel monochromatic light from a point source, such collimation of light being essential. The simplest procedure is to flex a thin slip of doubly silvered mica into a cylindrical shape. In such a case straight-line fringes somewhat resembling those of a Lummer plate are the result. If the thin film is in the form of a spherical shell (for example, a blown thin film of glass) circular fringes form, resembling Fabry – Perot rings. Under suitable conditions, the fringes are critically localized and appear on a screen suitably placed. Both the mode of formation and the plane of localization are indicated by , where, for simplicity, refraction effects are disregarded. The detailed theory will be published elsewhere, and main conclusions only are given here.