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why the width of dark ring decreases as we go away from the center in Newton's rings experiment?
Newton's Rings are a phenomenon observed when a plano-convex lens is placed on top of a flat glass surface. When viewed under monochromatic light, a series of concentric rings of alternating bright and dark colors are seen.
This is due to the interference of light waves. When the light waves reflected from the top and bottom surfaces of the lens are out of phase, they cancel each other out, resulting in a dark ring. As the distance from the center increases, the difference in path length between the two waves also increases, causing the dark ring to widen.
The width of the dark ring is affected by the wavelength of the light used, the radius of the lens, and the refractive indices of the lens and the medium it is placed on. It is also influenced by the thickness of the air gap between the lens and the surface, which can change with temperature or pressure.
Newton's Rings demonstrate the principles of interference, which is when two or more light waves interact and either amplify or cancel each other out. The phenomenon also highlights the wave nature of light and the concept of path difference, where the difference in distance traveled by two waves determines their interference pattern.
Newton's Rings have practical applications in the field of optics, particularly in the measurement of small distances and the testing of optical surfaces for quality and flatness. The phenomenon is also used in the manufacturing of lenses and other precision optical instruments.