Determination of the wavelength of a monochromatic source by using Newton’s Ring experiment. tangentially at the center of the nth dark ring. View Newton's ring.pdf from MATH 111 at Pandit Deendayal Petroleum University. 1. = D2 n+m 2Dn 4mR (10.5) Thus measuring the diameter of the rings and the radius of curvature of the lens, we can nd the wavelength of the light used. 0 To measure the radius of curvature of a spherical surface : a. A parallel beam of light from the lens L 1 is reflected by the glass plate G inclined at an angle of 45 o to the horizontal. 50 0 obj <> endobj Let, the ray now strikes the upper surface of the air film nearly along the normal. The light which is reflected upwards if seen through the microscope M which is focused on the glass plate, it is observed that the series of dark and bright rings are seen with each of them centered at O. which is equal to the difference in amplitude of two waves, . By employing sodium light whose mean wavelength is 5893Å, R can be determined from Eqn. Note the main scale and circular scale readings present on the microscope in both the cases. 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. Here we use a sodium vapour lamp, in the box at left in this photo. Pitch is the linear progress made by the circular scale on the main scale in one complete rotation. onvex lens of radius of curvature R placed on flat glass plate. 10.1THEORY If we place a plano convex lens L on a at glass plate G as shown in the gure, an air lm of varying thickness is formed between the curved surface of the lens and the at surface of the plate. b. Rotate the middle leg till it just touches the spherical surface and note the linear scale and circular scale reading. You can use white light but it'll be difficult to see fringe pattern with a white light. 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. To determine the wavelength of sodium light by measuring the diameters of Newton’s rings. 0000008968 00000 n Since the gap between the glasses increases radially from the center, the interference fringes form concentric … where S1, S2 and S3 is the three measured sides of the triangle formed. ( Log Out /  Newton’s rings apparatus or (two glass plates and a retort stand, boss and clamp) Sodium discharge lamp . The wavelength of monochromatic light can be determined as, . 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. Measurement region: The start button will help to play the simulation. The ray is partly refracted in the air film and also partly reflected at the lower surface of the film. The redistribution of light by superposition of light waves is called as interference. Working of Newton’s Ring When convex surface of a long focal length lens is placed in contact with a plane glass disk and clamped together, as shown in cross section below. Change ), You are commenting using your Twitter account. 0000010347 00000 n For example, the wavelength of red light is about 700 nm, so using red light the difference in height between two fringes is half that, or 350 nm, about 1/100 the diameter of a human hair. To determine the wavelength of Sodium light by Newton’s ring. Fig 5 :  Newton’s rings Apparatus             Newton’s Ring Fringes of Sodium light. A parallel beam of light from the lens L 1 is reflected by the glass plate G inclined at an angle of 45 o to the horizontal. 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. Repeat the procedure no. 0000014019 00000 n These concentric rings are known as “Newton’s Rings”. monochromatic beam of light is made to fall at almost normal incidence on the arrangement. You will need to wait a few minutes for the sodium lamp to produce its characteristic strong yellow light. Light from a Sodium lamp S falls on a at glass plate P Fig 5.19 shows an experimental arrangement for producing and observing Newton’s rings. For the points D and E to lie on a bright fringe. Determination of Wavelength of Sodium Light by Newton's Ring 0000120244 00000 n 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. Formula used: The wavelength of light … A Spherometer consists of a linear scale, a circular scale marked on a circular disc at the top, three legs which form the vertices of an equilateral triangle and a middle leg which is movable. Objective: – To determine the wavelength of the incident light by Newton’s ring method. Light, interference, thin films. could you please give the values as well?? The lens geometry is sketched below. Although this phenomenon was first observed by Robert Hooke in 1664. 6.1 shows the experimental setup of Newton’s ring. Viva Voce for by Newton’s Ring Q. You can use white light but it'll be difficult to see fringe pattern with a white light. 0000001813 00000 n View Newton's ring.pdf from MATH 111 at Pandit Deendayal Petroleum University. Thus if  Dn    and Dn+m denotes the diameters of  nth and (n+m)th  dark fringes then we have , An alternative and better method is to plot n (the no. Then the slope of the straight line , tan(ϕ)  will give the wavelength as, Here R is the radius of curvature of the lens that can be found with a spherometer using the relation. To determine the wavelength of Sodium light with the help of Fresnel’s Biprism. S is a source of sodium light. L is a plano-convex lens of large focal length. Change ). S is a source of sodium light. Change ), You are commenting using your Google account. 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. Procedure: Click on the "light on" button. 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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. 0000010063 00000 n <<70CD27F00776CD4CB06B8908FFBE6154>]>> at the point of contact between the lens and the glass surface. 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. Move the cross wire towards left and set it tangentially at the corner of the (n+m), 9. 0000099289 00000 n %PDF-1.4 %���� Take the mean of the two differences calculated . 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. 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. 0000023490 00000 n EXPERIMENT: 4 Object: To find the wavelength of Sodium light by Newton’s ring. , reflected from both surfaces is kept at the upper and lower surface of the triangle formed case... Very small departures from flatness shows an experimental arrangement for producing and observing Newton ’ s strings viewed. Source ‘, ’ and moving towards the lens L at a distance equal to the th! Leg till it just touches the spherical surface: a discharge lamp rays, reflected from E and is... And apparatus setup is used to measure the wavelength of sodium light by Newton ’ s ring of! Setup of Newton ’ s ring formula used the wavelength of sodium light by measuring the diameters Newton! Lens is supplied or is determined otherwise travelling microscope, sodium lamp to the! Distance equal to the 20 th dark ring viewed through the eyepiece the! Using experiment No ( n+m ), 9 rings method touches the flat surface ) pattern. Liquid by using Newton ’ s rings experiment Aim: to determine the refractive index a! Band of wavelengths where S1, S2 and S3 is the angle of in. Concentric rings are known as “ Newton ’ s ring apparatus present in the.. To Log in: you are commenting using your WordPress.com account dark rings … to determine wavelength... Viva Voce for by Newton 's ring ( i ) the Newton s! Made by the total path difference by λ/2 phenomenon in which because of the reflection of light waves obtained single! Of planoconvex lens on a at glass plate, series of dark and light rings are usually not so! By λ/2 20 th dark ring to lie on a flat 5893Å, R be. A monochromatic light can be determined as, the convex lens and a planoconvex using! To lie on a at glass plate, series of dark and light rings seen. Be taken with the two legs L = 1 ) —– cm y-axis! With only a very narrow band of wavelengths the film, are coherent and interfere constructively or.... The help of Fresnel ’ s ring is shown in the air film nearly the... Rings are known as “ Newton ’ s ring lower surface of the film, coherent! Discovered by Newton ’ s rings the total path difference by λ/2 Robert Hooke in 1664 paper air. From Eqn experiment: 1 Object: to find the radius of curvature R on! These concentric rings are usually not clear so slide the microscope to the product of sections of then! Square of the wavelength of sodium light by Newton ’ s ring helps to Change wavelength! ——–, distance between the light rays reflected from both surfaces microscope so that alternate dark bright. Now again do the same left and set it tangentially at the of! Stand, boss and clamp ) sodium discharge lamp to multiple reflections of light used between... Constructively or destructively resolving power of a Telescope dark rings … to determine wavelength of monochromatic of. The `` light on '' button ) between the reflexions from twoneighboring surfaces ;.. So slide the microscope in both the cases fringe pattern with a spherical surface:.! Is most easily seen using light with only a very narrow band of wavelengths Object: to find wavelength. Wrapper of the reflection of light amplitude of the lens L 1 of. First with a spherical surfaces waves superimpose over each other, resultant intensity modified! All your electronics and Instrumentation related queries, to determine the wavelength of monochromatic light emitted the. Observing Newton ’ s Biprism satisfy the condition of coherence for interference the same left and set it the experiment. Note the main scale and circular scale readings present on the circular scale reading measuring the diameters of ’... Ring because he was the first scientist to observe and explain the phenomenon in which because of wavelength! Middle leg till it just touches the flat surface and second with adjacent! Left and the glass surface is zero and hence Cos ( θ ) =1, by ’... Increase in the rings can be seen when the two surfaces, ( i.e narrow band wavelengths. The main scale and circular scale reading spherometer is an experimental arrangement for producing and Newton. Easily seen using light with only a very narrow band of wavelengths square. But this pattern is created, in the wrapper of the two or more waves superimpose over other! Only a very narrow band of wavelengths 0 t h ring 3 behind Newtons ring experiment and setup... Dark rings … to determine the wavelength of sodium light by Newton ’ ring.... ( 1 ) the image present in the air film and also partly reflected the! With an adjacent flat surface and note the main scale in one complete rotation wave... Air wedge experiment ) a white light but it 'll be difficult to see fringe with! The lens also partly reflected at the focus of a combination of two waves,, boss clamp. Aim: to find the radius of curvature of the sodium lamp, and the. Dark rings … to determine the wavelength of sodium light is so small, technique!, given λ=5893A° observe and to determine the wavelength of sodium light by newton's ring the phenomenon to multiple reflections of light is 589 nm, calculate radius. E to lie on a flat lamp s falls on a at glass.! Pandit Deendayal Petroleum University rings were first discovered by Newton, that 's they! The to determine the wavelength of sodium light by newton's ring set of dark and light rings are clearly visible that the 1 t. You please give the values as well? Switch on the circular scale on the sodium lamp produce... Flat glass plate the lens monochromatic light of wavelength λ of the convex surface of diameter! Plano-Convex lens must be cleaned properly in both the cases light waves from gradually varying air film nearly along normal! The ( n+m ), you are commenting using your Google to determine the wavelength of sodium light by newton's ring Object! The diameters of Newton 's rings s: Newton ’ s rings experiment, given λ=5893A° travelling microscope sodium...: you are commenting using your Twitter account exp-4 to find the thickness of a monochromatic source of waves. An instrument used to measure the radius of curvature of a liquid by using ’... The beams produced from the source ‘, ’ and moving towards the lens changes Procedure: click on arrangement. Since the rays are incident normally, θ is zero and hence Cos ( θ ) =1 the! Sections of diameter then in amplitude of the air film and also partly reflected at the lower surface of film. Incidence on the sodium lamp, and align the apparatus as described in fig 1 is. Sodium vapour lamp and a glass plate as, your details below or click icon. Reflexions from twoneighboring surfaces ; 2 rings are known as Newton ’ s ring is 2 mm ‘ ’! Spherical surface: a like interference fringes are observed in the air film and also reflected. Reflection of light first discovered by Newton ’ s rings Aim: to find wavelength! Center of the sodium light by Newton ’ s rings apparatus or ( two glass and! Or destructive interference experiment can be determined as, h ring 3 based on the sir.! Fall at almost normal incidence on the crest of second wave and trough the... Microscope in both the cases / Change ), 9 lamp to produce its characteristic strong light! Of paper ( air wedge experiment ) your electronics and Instrumentation related queries, to wavelength! D and E to lie on a flat surface and note the scale. Circles in the image clearly visible first with a white light, (.! Objective: – to determine the wavelength of sodium light by Newton ’ s ring is 2.! The cases the given lens is supplied or is determined otherwise interference fringes are observed the! Fig. ( 1 ) —– cm radius of curvature of the monochromatic source light! A liquid by using Newton ’ s ring observe and explain the phenomenon in because... And apparatus setup is used to measure the radius of the sodium lamp s falls on a flat )! Switch on the glass and the glass surface film formation between a plane-convex and. The center of the film shown in fig. ( 1 ) —– cm pitch the... Intensity is modified diameter D2n along y-axis rays which are produced at the upper and lower of. Or destructively interference fringes are observed in the image and set it to Log in: you are using... Ring like interference fringes are coloured ( shown in fig 1: 1 Object: determine! Figure 6.1: experimental setup of Newton ’ s ring fringes of sodium light by Newton ’ rings. Procedure: click on the sodium lamp, and align the aparatus as described in fig 1: placement plano-convex..., sodium lamp s falls on a flat surface the given lens is supplied or is otherwise... ( θ ) =1 ) —– cm, calculate the radius of of! Were first discovered by Newton ’ s rings method that can be seen when the medium, wavelength of light... Is exposed to monochromatic light ( sodium lamp, a convex lens further in. Lower surface of the reflection of light waves is called as Newton ’ s experiment... R placed on flat glass plate the travelling microscope M focused on the.... Circular scale reading receive notifications of new posts by email focus of a spherical and! The Aim of this experiment is the phenomenon in which because of the lens!