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# what is the condition for bright ring in newton's experiment?

Monochromatic light with a wavelength of 648 nm shines down on a plano-convex lens … So, it should appear bright. Move the microscope to left and record the position of the next bright ring. In Newton's ring experiment the diameter of n th and (n+8) bright rings are 4.2mm and 7mm respectively. while the wave reflected at the spherical surface of the lens has not suffered any phase change. Radius of curvature of lower surface of lens is 2m. When viewed with a monochromatic source, it appears as a series of concentric, alternately bright and dark rings centered at the point of contact between the two surfaces. The interference conditions for reflection and transmitted light are complementary. If the radius of curvature of the lens is 100 cm, find the wave length of the light. Here, l is the mean length of the three sides of the equilateral triangle formed by joining the tips of three outer legs, and h represents the height of the central screw above or below the plane of the outer legs. Then, the diameters of the two rings are given by, Subtracting the two equations and rearranging. Then ST = AO = PQ = t. Let rn be the radius of the nth dark ring which passes through the points S and P. If ON is the vertical diameter of the circle, then by the law of segments, (i) Using the method of Newton’s rings, the wavelength of a given monochromatic source of light can be determined. PY2107 Newton’s Rings Experiment 5 _____ 2.2 To see how Newton’s Rings can be used to measure the wavelength of light, consider ... condition for positive or negative interference, we must calculate the path difference, t (= BD). A.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. Fig 5.19 shows an experimental arrangement for producing and observing Newton’s rings. 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. For the m th ring: [(0.14x10-2) 2]/R = mx589x10-9 The rings in the fringes are called Newton’s rings. (b) How many rings would be seen if the arrangement were immersed in water (n = 1.33)? Alternate bright and dark circular rings with dark spot as centre is seen. … But the wave reflected from the denser glass plate has suffered a phase change of. Light from a monochromatic source (e.g., sodium lamp) is allowed to fall on a convex lens through a wide slit, which renders it into a nearly parallel beam. A monochromatic source of light S is kept at the focus of a condensing lens L 1. It is named after Isaac Newton, who investigated the effect in his 1704 treatise Opticks.When viewed with monochromatic light, Newton's rings appear as a series of concentric, alternating bright and dark rings centered at the point … Newton’s rings are formed by the interference phenomenon when monochromatic and coherent rays of light are reflected from the top and bottom surfaces of this air film. 44 In Newton’s rings experiment, bright and dark rings are obtained using sodium light. Article was last reviewed on Tuesday, July 7, 2020, Your email address will not be published. They arise from the interference of light. If white light is used instead of monochromatic, the lens system produces colorful interference, since the condition for a maximum in the interference is dependent on the wavelength. An important application of interference in thin films is the formation of Newton’s rings. This is the basic question related to newton ring experiment. A. When the two or more waves superimpose over each other, resultant intensity is modified. … Reproduction in whole or in part without permission is prohibited. Q. It is interesting to note that these interference fringes, which demonstrate the wave nature of light, should be credited to Newton who was the chief pro-ponent of the corpuscular theory. So, in a Newton's rings pattern in transmission are like negative images of those seen in reflection: a bright patch at the centre followed by a dark ring, then a bright, etc. What are interference fringes? The convex surface of a plano-convex lens having a long focal length (large radius of curvature) is placed in contact with a plane glass plate and clamped together. If the wavelength of sodium light is 589 nm, calculate the radius of curvature of the lens surface. This article is a description of Sir Isaac Newton’s Laws of motion and a summary of what they mean. (a) How many bright rings are produced in the reflected rays? If you have any queries please contact me. Condition for Minima (Dark Fringe): The effective path difference; substituting this in equation 2.21 ….2.23 . Interference occurs between the two waves which interfere … This lecture is useful for B. To control the thickness of paint that is used on posters. Hence the fringes are circular in shape. These rings are known as Newton’s rings. A.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. When the refracted ray strikes the glass sheet, it undergo a phase change of 180 O on reflection. Basic Methodology: A thin wedge shaped air film is created by placing a plano-convex lens on a flat glass … 1. The thickness of the film is zero where the lens and the plate are in contact with each other. Newton’s rings are observed by keeping a spherical surface of 100 cm radius on a glass plate with isopropyl alcohol. Nearly monochromatic source of light (sodium light), For testing the uniformity of a polished surface by studying the interference pattern the surface makes when placed in contact with a perfectly flat glass surface. Newton’s rings: It is a special case of interference in a film of variable thickness such as that formed between a plane glass plate and a convex lens in contact with it. The Newton’s rings experiment is set up as shown in Fig. movement of the microscope passes through the bright ring and is tangential to it. Let R … When viewed with monochromatic light , Newton's rings appear as a series of concentric, alternating bright and dark rings centered at the point of contact between the two surfaces. 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. Newton’s rings have been named after English physicist and mathematician Sir Isaac Newton, who was the first to observe the effect in 1704. Newton's ring experiment mainly contains following questions… Q.What are Newton’s Rings? 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 λ / 2 is introduced. I was asked to do a lab report in my University about Newton's rings experiment that we made in lab. Let, (i) Using the method of Newton’s rings, the wavelength of a given monochromatic source of light can be determined. Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail. All the bright and dark fringes are the loci of the points of the film of equal thickness. The phenomenon is caused by the interference of light waves—i.e., the superimposing of trains of waves so that when their crests coincide, the light … When viewed with white light, the fringes are coloured (shown in the wrapper of the text book). Q. the newton's rings are formed due to the phenomenon of thin film interference. An air film of varying thickness is formed between lens and the glass sheet. Define the interference pattern formed in Newton’s rings experiment (Recall Level). Taking into account the phase change of 180° for reflection at the rare to the dense surface, the conditions for constructive and destructive interference are, 2t = (m+1/2)λ (for constructive interference or bright rings), 2t = (m+1/2)λ (for destructive interference or dark rings), where m is the order of the ring and can take the values m = 0, 1, 2, 3, …, n, If R is the radius of curvature of the lens and r is the distance of the point under consideration to the point of contact of the lens and glass plate, then. Ans. Thus, it travels a total path 2t. These rings are known as Newton’s rings. Save my name, email, and website in this browser for the next time I comment. Fig 5.19 shows an experimental arrangement for producing and observing Newton’s rings. The diameters of the bright rings calculated for transmitted light using the equations above correspond precisely to the diameters of the dark rings in reflection. Hence, there is no path difference between the interfering waves. The sources should lie very close to each other … Thus, the wavelength λ can be determined from this equation. The rings are concentric circles. But the wave reflected from the denser glass plate has suffered a phase change of π while the wave reflected at the spherical surface of the lens has not suffered any phase change. A central dark fringe can be located between the glass plate and a lens. At point of contact t = 0 therefore the effective path difference ∆ = λ/2 which is odd multiple of λ/2 Therefore the Central fringe is dark. It is also used to find refractive index of unknown liquid. Newton gave the following list of colours from the centre outwards: First order: Black, blue, white, yellow, orange, red. At the point of contact the thickness of air film is zero and the path difference is also zero and as a 180 O phase change occurs, so they cancel each other and a dark ring is obtained at the centre. Copyright © 2018-2021 BrainKart.com; All Rights Reserved. Light is reflected from the upper surface of the glass plate and the lower surface of the lens. PC and camera for this experiment Introduction Newton’s rings are interference fringes of equal thickness which are produced in the air ﬁlm be-tween a convex surface and an optical ﬂat. 5885 A 0 B. To determine the wavelength of the given source. These viva questions will help you in your experiment to understand it better. The formation of Newton’s rings can be explained on the basis of interference between waves which are partially reflected from the top and bottom surfaces of the air film. In a Newton’s rings experiment the diameter of the 15 th ring was found to be 0.59 cm and that of the 5 th ring is 0.336 cm. Newtons Ring. Newton’s rings are interference fringes of equal thickness which are produced in the air ﬁlm be- tween a convex surface and an optical ﬂat. This is because light waves are randomly generated every … When the refracted ray strikes the glass sheet, it undergoes a phase change of 180° on. 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. 43 In Newton’s rings arrangement, if the distance between the lens and the plate is increased, the order of the ring at a given point _____. Determination of the wavelength of a monochromatic source by using Newton’s Ring experiment. fn next section, the method is explained in detail. Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build … At the point of contact of the lens with the glass plate, the thickness of the air film is minimal compared to the wavelength of light. Repeat it till you reach to the tenth bright ring on the left. Ans. Newton’s rings are a phenomenon that can be viewed daily. Hence, there is no path difference between the interfering waves. The most commonly seen interference is the optical interference or light interference. Hence the point O appears dark. What are the uses of Newton's ring experiment ? What do you mean by interference of light? These rings are known as Newton’s rings. 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. Record the microscope position from the horizontal scale along with its number with bright ring around the central dark spot as the first bright ring. The phenomenon of the formation of Newton’s rings can be explained based on the wave theory of light. Newton’s ring is a process in which Circular bright and dark fringes obtained due to air film enclosed between a Plano-convex lens and a glass plate. When light of wavelength λ = 646 nm is incident normally, 53 bright rings are observed, with the last one precisely on the edge of the lens. In a Newton's rings experiment, ... What is the diameter of the fifth bright ring? Newton’s rings . These circular fringes were discovered by Newton and are called Newton’s rings. In this video, I have explained, why the centre in the newton ring is dark? Watch the video completely and with attention. Ans.) When 650-nm light is incident normally, 55 bright rings are observed with the last one right on the edge ofNewton’s Rings page 6 of 7 Tuesday, May 22, 2012 Baghdad University – College of Science – Department of Physics – Optics Laboratory Administration Tele: … Newton’s rings, in optics, a series of concentric light- and dark-coloured bands observed between two pieces of glass when one is convex and rests on its convex side on another piece having a flat surface.Thus, a layer of air exists between them. Every fringe is the locus of points having equal thickness. At first, light falls on a glass plate inclined at an angle 45° to the vertical before reaching the lens-plate system at the bottom. 1st law of motion 2nd law of … Experimental arrangement for newton rings experiment: The experimental setup for Newton’s rings is shown in the figure. Q. Images of Newton's Rings s In a Newton’s-rings experiment, a plano-convex glass ( n =1.52) lens having radius r = 5.1 cm is placed on a flat plate as shown in the figure. Two sources should be very narrow . 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. When monochromatic light falls over it normally we get a central dark spot surrounded by alternatively bright and dark circular rings. 12.) If te have described a method to utilize the same set up to find the thickness of thin films. A monochromatic source of light S is kept at the focus of a condensing lens L1. If the radius of Plano convex lens is 100 cm, compute the wavelength of light used. Condition of Maxima (Bright Fringe): The effective path difference; substituting this in equation 2.21 ….2.22. … The condition for brightness is, Path difference, The thickness of the air film at the point of contact of lens L with glass plate P is zero. The redistribution of light by superposition of light waves is called as interference. Let us consider the vertical section SOP of the plano convex lens through its centre of curvature C, as shown in Fig 5.20. This is the basic question related to newton ring experiment. Stack Exchange Network . The interference pattern in which the positions of maximum and minimum intensity of light remain fixed with time, is called sustained or permanent interference pattern. If a liquid of refractive index μ is introduced between the lens and the plate, then the path difference is given by 2μt. Yet we don’t see interference patterns everywhere. 0. In this video, I have explained, why the centre in the newton ring is dark? I understand that the aim of the experiment is to measure the wavelength of a light after the formation of Newton's rings and I understand the mathematical derivation of formulae used for that (relation between radius and wavelength due to constructive or destructive interferences). The radius of nth dark ring and (n+m)th dark ring are given by. It was a difficult experiment since his source was not even close to being monochromatic, but Young's double-slit experiment provided the first indisputable evidence of light acting as a wave. When the air film is illuminated by monochromatic light normally, alternately bright and dark concentric circular rings are formed with a dark spot at the center. Diameter of Newton’s 15 th ring (D 15) = 0.59 cm = 0.59×10 –2 m When viewed with monochromatic light, Newton's rings appear as a series of concentric, alternating bright and dark rings centered at the point … Interference occurs between two waves that interfere constructively if path differences between them is (m+1/2)λ and destructively if the path difference between them is mλ, thereby producing alternate bright and dark rings. 2. While Newton’s laws of motion may seem obvious to us today, centuries ago they were considered revolutionary. When a plano-convex lens is placed over a flat glass plate, then a thin air layer is formed between glass plate and a convex lens. He used sunlight passing through two closely spaced slits. Condition for destructive interference: d = (m + 1/2) l. The first person to observe the interference of light was Thomas Young in 1801. In the Newton’s rings system, the fringes at the centre are quite broad, but they get closer as we move outward why is it so? Newton's ring pattern is … Let us consider the vertical section SOP of the plano convex lens through its centre of curvature C, as shown in Fig 5.20. Radius of curvature of lower surface of lens is 2m. It is named after the Scientist, Sir Isaac Newton. 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. Types of Blood Cells With Their Structure, and Functions, The Main Parts of a Plant With Their Functions, Parts of a Flower With Their Structure and Functions, Parts of a Leaf With Their Structure and Functions. Combine this result with the condition for the mth and nthdark rings. What the . Required fields are marked *. APPLICATIONS OF NEWTONS RINGS Newton’s rings experiment is used to determine the radius of curvature (R) of given lens by knowing the wavelength or vice versa. The key idea behind Newtons ring experiment is the thin film formation between a plane-convex lens and a glass plate. A series of rings formed in Newton's rings experiment with sodium light was viewed by reflection. In the Newtons ring experiment, determine the diameter of the \$20^{th}\$ ring if the diameters of the \$4^{th}\$& \$12^{th}\$ rings are 0.4 & 0.7 cm respectively. The apparatus is set up as … 3. If. Q.How are Newton s rings formed? Newton’s rings, in optics, a series of concentric light- and dark-coloured bands observed between two pieces of glass when one is convex and rests on its convex side on another piece having a flat surface.Thus, a layer of air exists between them. Follow via messages; Follow via email; Do not follow; written 3.0 years ago by neeta.vanage • 200: modified 2.9 years ago by Manan Bothra • 40: Follow via messages ; Follow via email; Do not follow; Subject: Applied Physics 2. 14. 4. You can also arrive at this conclusion from conservation of energy: where the energy is not reflected, it must be transmitted, so bright rings in reflection correspond to dark rings in transmission, and vice versa . 3.) An air film of varying thickness is formed between the lens and the glass sheet. The wavelength of light used is 5880 A 0. In a Newton’s rings experiment the radius of curvature R of the lens is 5 m and its diameter is 20 mm. The equation for wavelength is given by, In a laboratory experiment, students are required to calculate the radius of curvature R of the lens. The thickness of the air film is zero at the point of contact and gradually increases outwards from the point of contact. All rights reserved. Condition for sustained interference . The mercury vapour high-pressure lamp with the double con-densator (focal length 60 mm) fitted, the lens holder with the interference filter, the Newton’s rings apparatus, the lens hol-der with the lens of focal length 50 mm and a transparent screen about 40 cm away from the lens are all set up on the optical bench. Newton’s rings are studied in transmitted light as well. Newton's Ring Experiment Theory. It is calculated by spherometer using the following relation. The phenomenon of interference of light waves is obtained from monochromatic and coherent rays i.e. In particular, the center of Newton’s rings is bright in transmitted light and dark in reflection. . The microscope is properly focused so that alternate bright and dark concentric circular rings are observed more clearly. If the diameter of the 15th bright ring is 0.60 cm, then diameter of 5th ring is? Experimental Arrangement: Let S be the extended source of … An air wedge film can be formed by placing a Plano-convex lens on a flat glass plate. Q.How are Newton’s rings formed? An important application of interference in thin films is the formation of Newton's rings. The concentric circles produced by the Newton's rings phenomenon typically are dark alternating with bright, with the dark beginning in the center. Ans. If the radius of curvature of plano-convex lens is much greater than distance ‘r’ and the system is viewed through the above, the pattern of dark & bright ring is observed. The modification in the distribution of intensity in the region of superposition is called interference. )Travelling microscope,a sodium lamp,newtons ring apparatus,a spherometer, a cone lens of short focal length . NEWTONS RING BY TRANSMITTED LIGHT Condition of maxima: 2µt=nλ Condition of minima: 2µt=(n+1/2)λ 10. 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. The wavelength of light used is 589 nm. Newtons ring experiment viva questions are listed here. The film’s thickness varies from zero at the point of contact to a finite value in the wedge-shaped region. The thickness of the air film at the point of contact of lens L with glass plate P is zero. When a plano-convex lens lies on top of a plane lens or glass sheet, a small layer of air is formed between the two lenses. Consequently, the interfering waves at the center are opposite in phase and interfere destructively. To set up and observe Newton’s rings. This is due to the fact that the radii of dark rings are proportional to square root of natural numbers while those of bright rings are proportional to square root of odd natural numbers. From these rays of same frequency and constant phase difference. Table of Contents. The thickness of the air film varies from zero at the point of contact to some value t. If the lens plate system is illuminated with monochromatic light falling on it normally, concentric bright and dark interference rings are observed in reflected light. Therefore, the path difference introduced between the interfering waves is zero, the condition of minimum intensity. Newton’s rings Aim of the experiment: To observe Newton rings formed by the interface of produced by a thin air film and determine the radius of curvature of a plano-convex lens. The diameter of the m th dark ring was found to be 0.28 cm and that of the (m + 10) th 0.68 cm. The plano-convex lens is circular. It is interesting to note that these interference fringes, which demonstrate the wave nature of light, should be credited to Newton who was the chief pro- ponent of the corpuscular theory. Newton’s rings are a series of concentric circular rings consisting of bright- and dark-colored fringes. How are Newton's rings formed ? ∴ The condition for brightness is, Path difference. By studying the pattern of concentric rings, it is possible to determine the wavelength of monochromatic light and the refractive index of a given transparent liquid medium present in a wedge-shaped film. When the air film is … When white light is used the rings would be coloured. Around the point of contact alternate bright and dark rings are formed. (BS) Developed by Therithal info, Chennai. Theory Ans. 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. At the beginning of the experiment … Describe how does the Newton’s ring changes when air medium is replaced by a liquid medium (Understand level) In-class . The air film formed is wedge shaped locus of point of intersection is equal to the thickness of circles . Why does the central region appear dark in newton rings? (Give your answer in decimal with 1 digit after the decimal point, using … An important application of interference in thin films is the formation of Newton’s rings. Ans. Why Newton rings are circular in shape? Dark and bright rings ar formed due to the presence of air film when Plano convex lens is placed on glass plate . 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. &RQYHQWLRQDOO\1HZWRQ¶V rings experiment is used to determine the radius of curvature of a plano convex lens. This can be seen from the formula r2 = (m + ½) λa, (3), as r2 α λ1. If ‘r’ be the radius of nth bright fringe To determine the wave length of monochromatic light: If ‘l’ be the wave length of sodium light and r n be the radius of nth dark ring. Watch the video completely and with attention. 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. ADD COMMENT 0. written 21 months ago by vermavarsha432 • 130: modified 21 months ago by Yashbeer ★ 540: Let POQ be the plano-convex lens placed on a plane glass plate AB. Due to the air film formed by the glass plate and lens, interference fringes are formed, which are observed directly through a traveling microscope. … When white light is used in Newton’s rings experiment the rings are coloured, generally with violet at the inner and red at the outer edge. © 2021 (Science Facts). 5880 A o C. 5890 A o D.5850 A o 34.Second glass plate in Michelson ‘s Interferometer is known as If t is the thickness of the air film at a point on the film, the refracted wavelet from the lens has to travel a distance t into the film and after reflection from the top surface of the glass plate, has to travel the same distance back to reach the point again. It can also be shown that the bright rings also gradually become narrower as their radii increases. A dark central spot is obtained when viewed by reflection. 2.) The phenomenon occurs as a result of interference between the light reflected by the two surfaces. [June 2005, Set No. Around the point of contact alternate bright and dark rings are formed. What is the radius R of curvature of the convex surface of the lens? Now, if the radius of curvature 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). Compare the interference fringe pattern due to different light sources and varying thin films (Analyse level) Students will be able to evaluate the refractive index of an unknown liquid using Newtons ring … Q. A.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. Hence the point O appears dark. Ans.) In a Newton’s-rings experiment, a plano-convex glass (n = 1.52) lens having diameter 10.0 cm is placed on a flat plate. These concentric rings are known as " Newton's Rings ". Laboratory Manual for Newton’s Rings Method –, Demonstrations in Optics : Newton’s Rings –, Investigation of Interference Patterns and Newton’s Rings-. When a plano-convex lens lies on top of a plane lens or glass sheet, a small layer of air is formed between the two lenses. Determine the wavelength of light used. 1. The parallel beam of light emerging from L1 falls on the glass plate G kept at 45o. newtons rings • 6.3k views. Difference between newton’s rings by reflected light and transmitted light. 13.) The two sources should be coherent . Then diameter of nth dark ring. It is named after Isaac Newton, who investigated the effect in his 1704 treatise Opticks. 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. newtons rings • 6.3k views. Let t be the thickness of the air film at S and P. Draw ST and PQ perpendiculars to the plane surface of the glass plate. I have to do an experiment to find out the radius of curvature of a lens using the Newtons ring method given that you know the wavelength of the monochromatic light used in the experiment. The light beam from source “S’ falls on the convex lens from where the rays become parallel and strike the glass plate ‘G’.The glass plate ‘G’ partly reflected the beam and partly refract toward the mirror. In practical application, Newton's rings can be used by lens makers to determine the quality of a lens. 33.In Newton's ring experiment, the diameter of the 15 th ring was found to be 0.590 and that of the 5 th ring was 0.336 cm. Determine the wavelength of light used. 15. fn section 2, data analysis is provided and thickness of few sample paper strips is determined. The experimental setup for Newton’s ring is shown in the figure above. A monochromatic source of light S is kept at the focus of a condensing lens L, The formation of Newton’s rings can be explained on the basis of interference between waves which are partially reflected from the top and bottom surfaces of the air film. 2] Sol: The given data are. Tech And B. Sc students. This can be seen from the formula r 2 = (m + ½) λa, (3), as r 2 α λ 1. Viva Voce for by Newton’s Ring Q. The radius of n, Fraunhofer lines - Fluorescence - Phosphorescence, Theories of light : Corpuscular theory, Wave theory, Electromagnetic theory, Quantum theory, Scattering of light : Tyndal scattering, Raman effect, Condition for sustained interference and Young's double slit experiment, Diffraction grating explanation with Theory, Polaroids explanation and Uses of Polaroid.