# to determine the wavelength of sodium light by newton's ring

Due to this thin film of air a path difference occurs in the waves which reflect from the lower surface of the lens and the top surface of the glass plate. If we take a white light then there we observe different colours at the center of the rings so that it is impossible to count the rings that is the reason we do not use white light.. Why we take diameters of two fringes to find out the wavelength of monochromatic light? Fig 1 : placement of plano-convex lens over a plane glass. 0000098270 00000 n 0000001176 00000 n Apparatus required: A Plano convex lens of large radius of curvature, optical arrangement for Newton's … 0000006640 00000 n Hence the total path difference between the two rays, reflected from E and F is. Formula used: The wavelength of light … The beams produced from the monochromatic source satisfy the condition of coherence for interference. Ans. 0000014019 00000 n The camera took the photo shown above right. Exp-2 To determine the refractive index of a liquid by using Newton’s rings apparatus. Determination of the Wavelength of Light. At the point of contact ‘O’ as shown in figure 5 , the thickness of the air film is nearly zero and it slightly increases as we move towards the corner of the lens. To determine the wavelength of sodium light by measuring the diameters of Newton’s rings. It is based on the phenomenon of interference of light waves obtained from single coherent. Newton’s Ring is the phenomenon in which because of the reflection of light with the two surfaces, (i.e. To determine the wavelength of sodium light by Newton’s ring. EXPERIMENT: 4 Object: To find the wavelength of Sodium light by Newton’s ring. Newton's rings seen in sodium light. Newton's rings is a phenomenon in which an interference pattern is created by the reflection of light between two surfaces; a spherical surface and an adjacent touching flat surface. 93 0 obj<>stream Now, take out the convex lens and the plane glass out from the case carefully and measure the radius of curvature of the convex lens and also the height of the convex lens with the help of the spherometer. 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… Apparatus: - A Plano-convex lens of large radius of curvature, optically arrangement for Newton’s rings, plane glass plate, sodium lamp and traveling microscope. Fig 4: Newton’s Ring Apparatus present in the lab. Newton's rings: An experiment to find the wavelength of the sodium light using Plano-convex lens, Sodium lamp and a travelling microscope is called as a Newton's ring experiment.. Precautions:. These concentric rings are known as “Newton’s Rings”. Newton’s Ring Apparatus; Cornus Interference Apparatus; Michelson Interferometer - Standard Model; ... To determine the wavelength of Sodium light and LEDs ( Red, Blue, Green, Yellow ) Let D m and D m+k be the diameters of the m th and (m+k) th dark ring respectively. Move the cross wire towards left and set it tangentially at the corner of the (n+m)th dark ring where m=0,1,2,3,….. .Now move the cross wire towards right and set it tangentially at the corner of the (n+m)th dark ring where m=0,1,2,3,….. . When we use a monochromatic source of light, the Newton’s Ring formed appears as a series of alternating dark and light concentric rings. View Newton's ring.pdf from MATH 111 at Pandit Deendayal Petroleum University. Pitch is the linear progress made by the circular scale on the main scale in one complete rotation. 4. where S1, S2 and S3 is the three measured sides of the triangle formed. Newton’s rings apparatus or (two glass plates and a retort stand, boss and clamp) Sodium discharge lamp . I know that we can determine the wavelength of sodium light using newton's ring experiment but can we use this method to determine wavelength of other monochromatic light source? (3), as in the present experiment. Physclips provides multimedia education in introductory physics (mechanics) at different levels. Place the spherometer on the surface . produced at the upper and lower surface of the film, are coherent and interfere constructively or destructively. was so helpful,,,exact,precise &excellent, why don’t we take a white light instead of monochromatic source, bcz white light made up 7 light it give a coloured rings. endstream endobj 51 0 obj<> endobj 52 0 obj<> endobj 53 0 obj<>/Font<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 54 0 obj[/ICCBased 77 0 R] endobj 55 0 obj<> endobj 56 0 obj<>stream Where, D m+p is the diameter of the (m+p) th dark ring and D m is the diameter of the m th dark ring. In a Newton's Ring experiment, the diameter of the 2 0 t h dark ring was found to be 5. To determine wavelength of sodium light using Newton’s Rings. Formula used: The wavelength of light is … 13 Newton’s rings Aim : To determine the wavelength of sodium light by Newton’s ring. onvex lens of radius of curvature R placed on flat glass plate. More. Issac Newton in 1717, first observed an interference pattern formed by the reflection of light between a spherical surface and an adjacent flat surface. When we use a monochromatic source of light, the Newton’s Ring formed appears as a series of alternating dark and light concentric rings centered at the point of contact between the lens and the glass surface. 0000014388 00000 n 0000008968 00000 n Thin film interference: A film is said to be thin when its thickness is about the order of one wavelength of visible light which is taken to be 550 nm. S is a source of sodium light. %%EOF Least count is the least possible measurement that can be taken with the help of an instrument. Convex lens 3 Formula Used The wavelength λ of the sodium light is given by the formula in case of biprism experiment. Take the mean of the two differences calculated . 0000004407 00000 n As ‘t’ is very small then t2 will be so small which may be neglected, then, The path difference between the two rays one reflected from E and the other from F (from figure) is. Focus the microscope so that alternate dark and light rings are clearly visible. 0000048375 00000 n To find the wavelength of Sodium light by Newton’s ring. Loads of thanks from many mamy guys out here . monochromatic beam of light is made to fall at almost normal incidence on the arrangement. 3. of rings ‘n’ along the x-axis and the square of the diameter D, http://en.wikipedia.org/wiki/Interference_(wave_propagation), http://en.wikipedia.org/wiki/Newton’s_rings, http://www.physicsclassroom.com/physics-tutorial/interference-of-waves, http://physical-optics.blogspot.in/2011/06/newtons-rings.html. The reflected rays which are produced at the upper and lower surface of the film, are coherent and interfere constructively or destructively. A monochromatic source of light S is kept at the focus of a condensing lens L 1. But this pattern is called as Newton’s Ring because he was the first scientist to observe and explain the phenomenon. 0000010895 00000 n Wave length of light (λ) = 500 nm = 500 × 10 –9 m. Number of the dark ring … Plot the graph between the no. To find the wavelength of sodium lamp used. first with a spherical surface and second with an adjacent flat surface) interference pattern is created. Determination of the wavelength of a monochromatic source by using Newton’s Ring experiment. The diameter of the 10 th dark ring is 2 mm. You will need to wait a few minutes for the sodium lamp to produce its characteristic strong yellow light. Using any of the two relations, we can find the wavelength of the monochromatic light used. According to the principle of superposition of waves – When two or more waves of same type are incident at the same point then the total displacement at that point is equal to the vector sum of the displacements of the individual waves. tangentially at the center of the nth dark ring. 0000001634 00000 n What do you mean by interference of light? ( Log Out /  0000001554 00000 n After measuring all the three sides take the mean of all the three sides. 8. 0000036813 00000 n When two or more waves having same source and same frequency (coherent waves) interact with each other, then the resulting phenomenon is known as Interference . To Determine the Wavelength of Sodium Light using Newton’s Rings Lm L3L2 L1 Rm Left hand side Right hand side Dc : Diameter of the central ring R1 R2 R3. According to the principle of superposition of waves – When two or more waves of same type are incident at the same point then the total displacement at that point is equal to the vector sum of the displacements of the individual waves. Move the microscope to make the crosswire tangential to the next ring nearer to the center and note the reading. To determine the focal length of the combination of two thin convergent lenses separated by a distance with the … PY2107 Newton’s Rings Experiment 5 _____ 2.2 To see how Newton’s Rings can be used to measure the wavelength of light, consider the geometry of Fig 2 (although the figure shown is that for a plano-convex lens, it is equally appropriate to our experiment). Constructive interference occurs when the phase difference between the waves is a multiple of 2π, whereas destructive interference occurs when the phase difference is an odd multiple of π. it is exposed to monochromatic light of wavelength λ normally. To determine the wavelength of Sodium light with the help of Fresnel’s Biprism. Because of the constructive interference between the light rays reflected from both surfaces, light rings are formed while the dark rings are formed because of the destructive interference. 0000019274 00000 n Apparatus: A nearly monochromatic source of light (source of sodium light), a plano-convex lens C, an optically plane glass plate P, an optically at glass plate G in-clined at an angle of 45 , a travelling microscope with measuring scale and a spherometer. To determine the focal length of the combination of two thin convergent lenses separated by a distance with the help of a Nodal – Slide and verify to the formula. By employing sodium light whose mean wavelength is 5893Å, R can be determined from Eqn. Now again do the same for the same set of dark ring. If the waves that enter the lens are of arbitrary phase, and of all possible wavelengths Newton's rings in transmitted and reflected white light . Figure shown is an experimental arrangement for the determination of wavelength of sodium light. Although this phenomenon was first observed by Robert Hooke in 1664. Procedure: Click on the "light on" button. x�b```g``y����w�A��bl,v�t��������0m�p^e��b����~}:��NǓ.�{ǹ"o(|7(�Y�m�*�����\1e��Ē;�A�ţ���@��84��]\\BCӠ���@��yV��b��?��ʹP�I��UC��������(�03�+�'�ja��}ISw���P��\�S�����c�W{���0��S��#�1�o�#˯pY1��j`e�D�[���7��@l Ć�w�iF ~` �`X� Figure 2 Setup: Switch on the sodium lamp, and align the aparatus as described in Fig 1. When the two or more waves superimpose over each other, resultant intensity is modified. 3 6 m m. If the radius of the planoconvex lens is 1 m, calculate the wavelength of light … microscope M which is focused on the glass plate, series of dark and bright rings are seen with. At the point of contact ‘O’ as shown in figure 5 , the thickness of the air film is nearly zero and it slightly increases as we move towards the corner of the lens. 1. To determine the wavelength of the given source. A convex lens of large focal length is placed in contact of a plane glass plate resulting in the enclosure of the thin air film between the glass plate and the lens. A sodium vapour lamp and a planoconvex lens on a flat. 0000002023 00000 n Note the main scale and circular scale readings present on the microscope in both the cases. Newtons ring experiment and apparatus setup is used to confirm the wave nature of light. Viva Voce for by Newton’s Ring Q. of divisions on the circular scale = ——–, Distance between the two legs l = 1) —– cm. Exp-4 To find the thickness of a thin sheet of paper (air wedge experiment). The first few rings are usually not clear so slide the microscope to the left or right and set it. The modification in the distribution of intensity in the region of superposition Objective: – To determine the wavelength of the incident light by Newton’s ring method. 0000008839 00000 n You will need to wait a few minutes for the sodium lamp to produce its characteristic strong yellow light. These rings are known as Newton’s rings. The superimposing waves can have constructive or destructive interference. Circular bright and dark rings … Move the cross wire towards left and set it tangentially at the corner of the (n+m), 9. Consider a ring of radius ‘r‘ due to thickness ‘t‘ of air film as shown in the figure 6 given below: r is the distance between D and E from the center B. t is the height between the chord of the circle and the plane glass plate. 3. 0000120244 00000 n 5. 0000023490 00000 n The lens geometry is sketched below. 4. 7. Light from a Sodium lamp S falls on a at glass plate P The ray is partly refracted in the air film and also partly reflected at the lower surface of the film. Newton’s Rings Experiment Aim: To determine the wavelength of monochromatic light (sodium light) using c. The initial reading is then calculated using the formula, IR = main scale reading + (circular scale reading*least count). Now consider a ring of radius r due to thickness t of air film as shown in the figure given below: ... of plano-convex lens is known and radius of particular dark and bright ring is experimentally measured then the wavelength of light used can be calculated from equation (3) and (4). Studying the interference phenomenon due to multiple reflections of light waves from gradually varying air film. Repeat it till you reach to the 20 th dark ring on the right. A beam of monochromatic light emitted from the source ‘S’ and moving towards the lens ‘L’ and then it is reflected from the lens ‘L’ to a sheet of glass ‘G’. 0000017738 00000 n When light is incident on such a film, a small portion gets reflected from the upper surface and a major portion is transmitted into the film. For an air film (µ = 1) between the lens and the glass plate. on the crest of second wave and trough of the first wave fall, sum of the amplitude of the two superimposing waves. Experiment 4 - To determine the wavelength of Monochromatic light (sodium light) by Newton’s Ring Experiment 5 - To determine the wavelength of sodium light source using plane transmission grating Experiment 6 - To verify Inverse square law of light using a photo cell. Fig 5.19 shows an experimental arrangement for producing and observing Newton’s rings. The wavelength of sodium light has been determined . In this case, the radius of curvature of the convex surface of the given lens is supplied or is determined otherwise. Exp-1 To determine the wavelength of sodium light. =R2¡2tR+t2+r. Apparatus used: A Plano convex lens of large radius of curvature, optical arrangement for Newton’s rings, plane glass plate, sodium vapour lamp and traveling microscope.