To determine the wavelength of sodium light by newton s ring method. For this reason, the surfaces are to be cleaned before the commencement of the experiment. The redistribution of light by superposition of light waves is called as interference. Newton s rings is a phenomenon in which an interference pattern is created by the reflection of light between two surfaces. May 22, 2012 in the current experiment, does light behave like a particle photons or like a wave or both. Newton s rings is analysed as an interference pattern and we derive the equation relating the lens radius of curvature to the radii of the dark rings. When a planoconvex lens is placed over a flat glass plate, then a thin air layer is formed between glass plate and a convex lens. Experiments in engineering physics physics lab manual fourth revised edition. Physclips provides multimedia education in introductory physics mechanics at different levels. Newtons ring experiment viva concepts apni physics. To determine the wavelength of sodium light using newtons. Ring shaped fringes are produced by the air film existing between the convex surface of a long focus planoconvex lens and the plane of glass plate.
With the help of travelling microscope measure the diameter of the n th dark ring. One can do this but it is difficult and you would need a great deal of patience and optical experimentation skill. Thin film interference with films of varying thickness newton s rings. Nb a highpressure sodium street lamp as used in colour studies will not give sharp fringes in this experiment. The user can view the effect of newtons rings formed when the medium changes. The simulation virtualizes the newtons rings experiment. In this experiment you will study the phenomenon of newton s rings, and use it to a measure the wavelength of light, and b the refractive index of water. If the centre fringe is not dark, try polishing the lens and flat with a spectacle cleaning cloth. The procedure requires us to measure the diameter of each ring we need to measure the diameter of at least 10.
Y0u can perform the experiment with a laser but to get a reasonable number of easily visible fringes you would need to increase the width of laser beam with a beam expander although a single lens could be used you will note that in the usual arrangement of newton s rings using a conventional light source, the source is a extended and not a point eg a sodium lamp often with a piece of ground. Newton s rings can be explained on the basis of wave theory of. To determine the radius of curvature of a plano convex lens using newtons rings methods 36. Newtons rings is a phenomenon in which an interference pattern is created by the reflection of. Consequently, the center of newton rings is dark due to destructive. Introduction newton s ring is the demonstration of the interference of light waves reflected from the surface of a thin air film formed between the plane glass and the convex lens whose. The phenomenon of newton s rings, named after isaac newton, is an interference pattern caused by the reflection of light between two surfaces a spherical surface and an adjacent flat surface. Find wavelength of sodium light by newtons rings youtube. There is a central dark spot around which there are concentric dark fringes. At the point of contact of the lens and the glass plate, the thickness of the film is effectively zero but due to reflection at the lower surface of air film from denser medium, an additional path of. Here we explain the phenomenon and analyse its geometry. An air film of varying thickness is formed between the lens and the glass sheet. Observation and calculations of newtons ring experiment. When a planoconvex lens is placed on the top of a flat glass surface a thin air film is formed between the two surfaces as shown in the figure.
Newtons rings and determination of the wavelength of light. Newton s ring experiment is a phenomenon in which the reflection of light between two surfaces is used to create an interference pattern. Isaac newton was the to first study the newtons ring pattern in 1717, so it was named as newtons rings. Is it on the glass plate surface or the surface of the convex lens. Different ring pattern can be seen by changing the radius of curvature of the lens and wavelength of light source components. Oct 22, 2007 newton s rings are a fun demonstration of the wave nature of light, and also of the fact that white light is made up of many components of different wavelengths. Abstract this experiment looks to investigate the physical optics of the interference pattern called newtons rings and calculate the wavelengths of various filters as well as the. In the lab, we perform newton s ring experiment with the help of sodiumvapour lamp. It is named after isaac newton, who investigated the effect in his 1704 treatise opticks. This is achieved when no more rings emerge from the ring centre when the adjusting. When the two or more waves superimpose over each other, resultant intensity is modified. Laboratory manual for newtons ring method background coherent sources of light, concept of interference, interference by division of wave front and amplitude, interference in thin lms, newtons ring apparatus. Determination of the wavelength of a monochromatic source by using newtons ring experiment. To determine the wavelength of sodium light by newtons ring.
The diameter of bright ring is proportional to square root of odd natural numbers spacing between fringes. Py2107 newtons rings physics 2107 newtons rings experiment 5. The experiment is performed when there is an air film between the planoconvex lens and the optically plane glass plate. The experimental setup used for the experiment is shown in fig. Newton observed these rings when placing a spherically shaped piece of glass a lens touching a flat piece of glass. The wavelength of monochromatic light can be determined as. To find the wavelength of sodium light by newtons ring. The question is, where do the fringes form in newton s rings. Newton s ring apparatus aim of the experiment to study the formation of newton s rings in the airfilm in between a planoconvex lens and a glass plate using nearly monochromatic light from a sodiumsource and hence to determine the radius of curvature of the planoconvex lens.
Using the newtons rings apparatus, to measure the diameter of the rings at different wavelengths and. In a newtons rings experiment, a planoconvex glass n 1. Introduction the formation of newtons rings is an important application of interference of light wave from the opposite faces of. If by chance, you get a bright central spot in your experiment, will you proceed with the experiment with the same system of fringes or will you reject. In this case, the radius of curvature of the convex surface of the given lens is supplied or. The centre of the ring dark in newtons rings experiment with reflected light is dark because at the point of contact the path difference is zero but one of the interfering ray is reflected so the effective path difference becomes. Jun 02, 2011 these concentric rings are known as newtons rings. The key idea behind newtons ring experiment is the thin film formation between a planeconvex lens and a glass plate. A plano convex lens of large radius of curvature, optical arrangement for newtons rings, plane glass plate, sodium vapour lamp and traveling microscope. In a newtons rings experiment the diameter of the 15 th ring was found to be 0. Alternate dark and bright rings formed due to presence of air film when plano convex lens is placed on glass plate is called newtons rings.
View newtons rings from phys 1222 at university of the west indies at st. The modification in the distribution of intensity in the region of superposition. When a light ray is incident on the upper surface of the lens, it is reflected as well as refracted. Experiment 3 to determine the specific rotation of cane sugar solution with the help of polarimeter experiment 4 to determine the wavelength of monochromatic light sodium light by newtons ring experiment 5 to determine the wavelength of sodium light source using plane transmission grating. The central ring should be dark throughout the experiment. Circular bright and dark rings are seen with the dark central fringe. Newtons prism experiment video physics khan academy.
Sample data table ring number lm j lm l1j rm j rm r1j dm 24 23 22 1 spherometer a spherometer is used to. In the traditional version of newton s rings, a slightly convex lens is placed above a flat glass plate or optical flat. This page supports the multimedia tutorial interference. Modules may be used by teachers, while students may use the whole. Apparatus required newton s rings apparatus, travelling microscope, sodium lamp, a convex lens and a spherometer. Ring like interference fringes are observed in the reflected light. In transmitted light the ring system is exactly complementary to the reflected ring system so that the centre spot is bright. Monochromatic light is used to illuminate the lenses. Video of a simple experiment with two lenses, and newtons rings on mica observed. Traveling microscope, sodium vapour lamp, planoconvex lens, plane glass plate, magnifying lens. The reason that the centre is almost always dark is that the classic newton s rings experiment simply involves putting the convex lens in contact with the reference optical flat. Pdf newtons rings is a phenomenon in which an interference pattern is created by the reflection of light between two surfacesa spherical surface and. View academics in newtons ring experiment on academia.
Newton s rings are interference fringes of equal thickness which are produced in the air. To determine the wavelength of sodium light by newtons ring method. A central dark fringe can be located between the glass plate and a lens. Newtons ringsformation of newtons ringsthin filmradius. In this experiment the radius of the curvature r of a convex lens was determined. An application of newtons rings experiment iopspark. The thickness of air film varies from zero at the point of contact to some value t at point p. In this optics experiment, a convex lens is placed on a reflecting surface.
Newton s rings are interference patterns formed by light incident on the thin film of air between a convex lens and a flat or between two suitable lenses. Schematic of a lens and a flat plate used to form newtons rings leok30 newton s ring experiment apparatus complete model note. The newtons rings are not equally spaced because the diameter of ring does not increase in the same proportion as the order of ring and rings get closer and closer as n increases. Newton s rings circular interference formed between a lens and a glass plate with which the lens is in contact. When a monochromatic beam if light coming from an extended source is incident on a combination of l and g as shown in fig. Whenever light travels from a medium of one refractive index to another medium of different refractive index, a fraction of incident light gets reflected and this is given mathematically by fresnels equations. Aim to determine wavelength of sodium light using newtons rings. When viewed with monochromatic light, it appears as a series of concentric, alternating light and dark rings centered at the point of contact between. Experiment, theory an important application of interference in thin films is the formation of newton s rings. Newtons rings page 7 of 7 tuesday, may 22, 2012 baghdad university college of science department of physics optics laboratory administration tele.
To determine the wavelength of sodium light using newtons rings table 8. Newtons ring is the phenomenon in which because of the reflection of light with the two surfaces, i. A nearly monochromatic source of light source of sodium light, a planoconvex lens c, an optically plane glass plate p, an optically at glass plate g inclined at an angle of 45, a travelling microscope with measuring scale and a spherometer. To observe newton rings formed by the interface of produced by a thin air film and determine the radius of curvature of a. Newtons ring experiment indian institute of technology. A thin air film is formed between the plate and the lens. When a plano convex lens of long focal length is placed over an optically plane glass plate, a thin air film with varying thickness is enclosed between them.
To determine wavelength of sodium light using newtons rings. The two interfering beams, derived from a monochromatic source satisfy the coherence condition for interference. If the radius of curvature r of the lens is much greater than the distance r. Newtons strings are viewed through the eyepiece of the travelling microscope m focused on the sir film. Placing the observation screen at the ump is critical to the experiment since. Setup and procedure the newtons rings experiment is set up as shown in fig. Newtons rings title newtons rings abstract in this. Newton s rings definition, the pattern of light interference produced by the contact of the convex surface of a lens with a plane glass plate, appearing as a series of concentric, alternately bright and dark rings, which are colored if the light source is white. Pdf newtons rings is a phenomenon in which an interference pattern is created by the. Newton s rings are a fun demonstration of the wave nature of light, and also of the fact that white light is made up of many components of different wavelengths. To determine wavelength of sodium light using newtons.
In newton s rings experiment the fringes formed are called rings rather than fringes, as these are circular in shap. To determine the wavelength of sodium light using newton s rings. They are formed as a result of interference between light waves reflected from the upper and lower surfaces of the air film developed between the convex surface of plano convex lens and plane glass plate. What is the procedure for newtons ring experiment answers. To observe newton rings formed by the interface of produced by a thin air film and determine the radius of curvature of a planoconvex lens.
Why cant we perform the same experiment with laser. Jun 10, 2014 newton s ring experiment demonstrates interference with a circular object. Please read additional instructions on the bench for setting up the pc and camera for this experiment. When monochromatic light is incident on a plano convex lensas shown in the picture, these dark rings are produced which are observed with the help of a travelling microscope. They are observed when light is reflected from a planoconvex lens of a long focal length placed in contact with a plane glass plate. Newtons rings is a phenomenon in which an interference pattern is created by the reflection of light between two surfacesa spherical surface and an adjacent touching flat surface.
Experiments in engineering physics bachelor of engineering and technology prepared by, p. A slightly convex lens is placed above an optical flat. If the radius of curvature of the lens is 100 cm, find the wave length of the light. To form newtons rings and then find the radius of curvature of a. Newtons rings 38 discussion i the newtons ring experiment can be also used to find the wavelength of a monochromatic light.
250 125 1492 928 639 1390 244 848 1146 1366 647 50 1101 113 791 913 1100 1106 574 1518 307 1297 411 904 912 178 744 703