History And Formation Of Newtons Rings

History And validation Of Newtons soundIn this experiment the physical property of perturbation of get by will be use to de edgeine the wavelength,, of a wake source. The handicap f rebounde system here is a praxis of coaxial circles, the diam of which you will measure with a travelling microscope (which has a Vernier scale). If a dust gibbous lens of the eye of the eye is position on a clean methamphetamine hydrochloride slide (optically straight) and viewed in monochromatic descend, a series of go may be work by means ofn around the picture of clear up in the midst of the lens and the slide. These go atomic number 18 known as Newtons go and they arise from the hoo-hah of light reflected from the nut surfaces at the air film in the midst of the lens and the slide. The experimental set-up is shown in figure 1.History of history of Newtons pluralityThe phenomenon of Newtons rings, named later on sir Isaac Newton who first studied them in 1717, Newtons r ings is a descriptor of intermeddlence caused by twain surfaces after saying of light a sphere surface and an adjacent flat surface. When view with monochromatic light its appears as a series of concentric, alternating glinting and shady rings revolve abouted at the augur of contact amongst the two surfaces. When we see with white light, it forms like a rainbow colours concentric ring pattern because the different wavelengths of light interfere at different heaviness of the spirit level between the surfaces. The light reflected from both surfaces caused by constructive interference, while the twilight(prenominal) rings are caused by destructive. Perhaps, the come oner rings are to a greater extent closely spaced than the inner.So the above phenomenon was first described by Robert Hooke in his 1664 book Micrographia although its name derives from the physicist sir Isaac Newton, who was the first to analyze it.Newtons ringsThe term Newtons rings is a ring form by the gla ss of curved, typically a umbel-like lens, is put in contact with a glass of a design surface. The curved glass kept on the plan glass, forming a film of air between them is increasingly larger along the length of the curve. When light is directed into the curved glass, a many of concentric circles appears. That is why the rings are referred to as Newtons rings. Which was the first to observe the phenomenon by Sir Isaac Newton?The Newtons rings formed will be phenomenon typically is dark alternating with bright, with the dark beginning in the center. It is formed as a result of interference between the light reflected by the two surfaces. Towards the application, Newtons rings can be used by lens start outrs to find out the quality of a lens. In a well-made lens, the rings should be uniform.When a umbellate surface with its Plano- convexo-concave lens is placed on a glass sheet, an air film of gradually increasing thickness outward-bound is formed between the lens and the sheet. The thickness of film at the academic degree of contact is zero. If light is allowed to fall on the lens, and the film is viewed in reflected light, substitute(a) bright and dark concentric rings are seen around the point of contact.(Source google.com)Newtons Rings, it is visible a pattern of light and dark circles when a convex lens is placed, curved side down, on top of a flat piece of glass. The pattern was first observed by Sir Isaac Newton. The rings are caused by interference of light waves.When a light is falls downward(prenominal) onto the two pieces of glass, two overlapping beams of light are formed-one from light reflected by the lower surface of the curved glass and the former(a) from light reflected by the upper surface of the flat glass. The light reflected from the vapid glass moves far than the light reflected from the curved glass. It depends on the distance between the two surfaces, light waves in the two beams may be in human body, and reinforcing each othe r or they may be out of phase, canceling each other out. Since the distances between the two reflecting surfaces increases with distance from the point where the lens and flat glass make contact, the areas where the waves are in phase and out of phase occur in concentric rings around the center of the lens.If the beam of light falls at the two pieces of glass is of a single wavelength i.e. monochromatic, the rings are tailor circles of a single color. The rings are fewer in number, just now highly colored when white light is usedFormation of Newtons RingsNewtons rings are formed as a result of interference between the light waves reflected from the top and female genitalia surfaces of the air film formed between the lens and glass sheet.The phenomenon of the formation of Newtons ring can be explained on the basis of wave theory of light i.e.An air film of varying thickness is formed between lens and the glass sheet.When a ray is incident on the surface of the lens, it is reflect ed as well as refracted.When the refracted ray strikes the glass sheet, it undergoes a phase change of 180 on the reflection.Interference occurs between two waves which interfere constructively if path divagations between them is (m+1/2) 1 and destructively if path unlikeness between them is ml producing alternate bright and dark rings.Radius of Newtons RingLet the roentgen of curvature of the convex lens is R and the spoke of ring is r. dig light of wave length l falls on the lens. later on refraction and reflection two rays 1 and 2 are obtained. These rays interfere each other producing alternate bright and dark rings. At the point of contact the thickness of air film is zero and the path difference is as well as zero and as a 180O path difference occurs, so they cancel each other and a dark ring is obtained at the centre.As we move away from the central point, path difference is also changed and alternate dark and bright rings are obtained. Let us suppose that the thickn ess of air film ist.By using the theorem of geometry,x = xr x r = t (2R t)= (2Rt -)Sincet is very dwarfish as compare to r, therefore neglecting = 2Rt r2 = 2Rt.. (1)In thin films, path difference for constructive interference is 2nt = (m+1/2) l Where n= refractive tycoonfor air n = 1Therefore, 2t = (m+1/2)l .. (2)For first bright ring m = 0for second bright ring m = 1For third bright ring m = 2SimilarlyFor nth bright ring m = N-1 lay the value of m in equation (2) 2t = (N-1+1/2)l2t = (N-1/2)l t =1/2 (N-1/2) l .. (3)Putting the value oft in equation (1)r2 = 2Rtr2 = 2R. 1/2 (N-1/2) lr2 = R (N-1/2) l=Where N is the bright ring number, R is the r of curvature of the lens the light is passing through, and is the wavelength of the light passing through the glass.Working of Newtons RingWhen convex surface of a long central length lens is placed in contact with a plane glass disk and clamped in concert, as shown in cross section below. trying on screws are tightened to secure intima te contact at the center.Between the two surfaces of glass a thin film of air is formed and when this band is viewed under reflected light from an lengthy light source. We ignore reflections from the top (Plano-convex lens) and bottom (plane glass disk) as these reflections just contribute to the overall glare. Since the wave is going away from a higher to lower refractive power medium, there is no phase change at the glass air surface of convex lens. Whereas at the air-glass surface of the plane disk suffers a half-cycle phase wobble due to reflection.Let R be the radius of curvature of the convex lens, r distance from center and the t air film thickness.Then, = 2RtAnd the radius of the bright ring is given by= (N + ) R Here the two glass surfaces are in close contact and there is no reflection because it is as if there were no surfaces. The reflected light is almost white in colour for first maximum, this is because the distance between the two glass surfaces is such that its almost () for the entire spectrum. Similarly succeeding rings exhibit much and more colour. Where the thickness is odd number N of (1/4) for green, and where sacrilegious is about(predicate) (N+1) (1/4) and red is (N-1) (1/4) will be most monochromatic ring. Therefore blue and red at reflection minima while green is at a reflection maximum.The experimental procedure to find the radius of Newtons bright ring is as follows.The convex surface of large radius of curvature is placed in contact with a plane glass disk and clamped togetherAdjustment screws are tightened to secure intimate contact at the centerA thin film of air is formed between the 2 surfaces of glassThe thin film of air is viewed under reflected light from an extensive light sourceReflections from the top ( Plano-convex lens) and the bottom ( plane glass disk) are ignored, since these reflections just contribute to the overall glareThe reflections of interest involves where the surfaces in contactSince the wave is going from higher to a lower refractive mightiness medium, there is no phase change at the glass-air surface of the convex lensWhereas at the air-glass surface of the plane disk suffers a half-cycle phase shift due to reflection.Taking R as the radius of curvature of the convex lens, the relation between the radius of the ring r and the air-film thickness t is given by r2 = 2Rt .Then radius of the nth bright ring will be given by =The Newtons ring is used to Illustrate the interference fringes formed in the air film between optical surfaces. Newtons rings are used to determine the radius of curvature of the bi convex or Plano-convex lens Measure the refractive index of a substance placed beneath the same lens. Determine the wavelength of sodium light