You can also arrive at this conclusion from conservation of energy: The lens geometry is sketched below. Phenomenon[ edit ] The phenomenon was first described by Robert Hooke in his book Micrographiaalthough its name derives from the physicist Isaac Newton, who was the first to analyze it.
There is a central dark spot around which there are concentric dark fringes. Around the point of contact alternate bright and dark rings are formed.
The reflected beam from the air film is viewed with a microscope. In this area, the thin film of air between the lens and the flat has a thickness much less than the wavelength of light. An extended interference pattern is most easily seen using light with only a very narrow band of wavelengths.
In white light, the rings are rainbow-colored, because the different wavelengths of each color interfere at different locations. This leads to the alternating rings of constructive interference bright rings and destructive interference darkas shown in the photograph.
Alternate bright and dark circular rings with dark spot as centre is seen. Consider a ray of monochromatic light that strikes the upper surface of the air film nearly along normal.
Light from a monochromatic single color source shines through the top piece and reflects from both the bottom surface of the top piece and the top surface of the optical flat, and the two reflected rays combine and superpose.
However the ray reflecting off the bottom surface travels a longer path. Therefore, the waves will reinforce add and the resulting reflected light intensity will be greater. So, provided the coherence length is sufficiently long, these rays give constructive interference in reflection.
Theory[ edit ] Closeup of a section of the top glass on the optical flat, showing how interference fringes form. Let R be the radius of curvature of the plano convex lens and O be the point of contact of the lens with the plane surface.
At positions where the path length difference is equal to an odd multiple of a half-wavelength athe reflected waves reinforce, resulting in a bright spot. The convex side of the lens has a radius of curvature R and we consider one of the rigns with radius r where the air film between lens and flat has thickness t.
The ray refracted in the air film is also reflected partly at the lower surface of the film. One surface is slightly convex, creating the rings. At right we see a photograph of the interference pattern. By means of a sheet of glass G, a parallel beam of monochromatic light is reflected towards the lens L.
Real materials are not infinitely rigid and so they deform at contact and may even weld together. Since the gap between the glasses increases radially from the center, the interference fringes form concentric rings. For illumination from above, with a dark center, the radius of the Nth bright ring is given by r.
When the air film is illuminated by monochromatic light normally, alternate bright and dark concentric circular rings are formed with dark spot at the centre. Next consider the middle set of rays in the sketch. This is surrounded by bright and dark circles, due to constructive and destructive interference respectively.
As a result, a bright area will be observed there. This interference results in a pattern of bright and dark lines or bands called "interference fringes" being observed on the surface. The thickness of the air film is almost zero at the point of contact O and gradually increases as one proceeds towards the periphery of the lens.
The large dark patch at the centre is around the point where the convex lens surface touches the glass flat below it. So the transmitted rays near the point of contact have constructive interference in transmission.
The thickness of the air film is zero at the point of contact and gradually increases outwards from the point of contact.A convex lens is placed above a flat lens, which produces rings of light and dark fringes (bottom). Explanation In the traditional version of Newton's Rings, a slightly convex lens is placed above a flat glass plate or optical flat.
Physics Assignment Help, Show phenomenon of the formation of the newtons rings, The phenomenon of the formation of the Newton's rings can be explained on the basis of wave theory of light. When a light ray iP1 from an extended monochromatic light source S is allowed to fall normally on the system (Plano-convex lenses L+ Plane gl.
Jun 02, · Newton's Rings Circular interference formed between a lens and a glass plate with which the lens is in contact.
There is a central dark spot around which there are concentric dark killarney10mile.com radius of the nth ring is given killarney10mile.com: Abdul Wali Khan.
The phenomenon of the formation of the: Newton's rings can be explained on the basis of wave theory of: light. An air film of varying thickness is formed between the lens and the glass sheet. When a light ray is incident on the upper surface of the lens, it is reflected as well as refracted.
NEWTON’S RINGS PowerPoint Presentation, PPT - DocSlides- INTRODUCTION. The formation of Newton’s rings is an important application of interference of light wave from the opposite faces of a thin film of variable thickness. Newton's rings setup; The geometry and the interference pattern; Reflections and the conditions for constructive and destructive interference; Newton's rings in transmission; The radius of the rings gives the radius of curvature of the lens; Newton's rings seen in sodium light.Download