Interaction of Light with Sound in a Crystalline Structure

Interaction of Light with Sound in a Crystalline Structure Lewis Allison Abstract The effects of altering the angle of incidence acoustic intensity were investigated using a lead molybdate crystal with a Piezo-electric transducer attached. A HeNe laser was used as a light source for the investigation. The angle of diffraction at which the first order beam was found to be 0.027 Rad  ± 0.009 Rad the acoustic intensity in the crystal at 140MHz was 14.3104 W m-2  ± 2.9104 W m-2. Introduction The interaction between of light sound has been observed investigated since ancient Greece. However, Leon Brillion a French-American physicist, was first to predict diffraction of light by sound in 1922(1). Bragg’s angle is given by the Bragg’s law(2-4) explains the scattering of electromagnetic waves both coherently incoherently through a crystalline structure. In this investigation the sound waves propagating through the lead molydbate(8) crystal change the refractive index. A photon at one instance may experience, for instance a refractive index of 2.3, where as a photon a moment later will experience a different refractive index from atoms in the crystal being displaced by the pressure of the sound wave(9). This means the photons will be travelling at different speeds through the medium, so when it emerges the beams of light then interact interfere with each other. This creates the maxima minima from the constructive deconstructive interference. Bragg’ s Law(4-7) describes the condition at which the constructive interference takes place. The source of the sound waves which propagate through the crystal is a Piezo-electric transducer. 140Mhz was applied to the transducer by the RF Driver which can alternate the magnitude of the sound wave produced. The transducer was mounted on a rotational stage allowing the effects of transmitted light intensity when the angle of incidence of the light onto the modulator crystal was altered. A HeNe laser was used in the experiment as the light source. A viewing screen was used, so the diffraction characteristics could be seen a metre rule was used to measure the distsance from the acousto-optic modulator to the viewing screen photo detector. Method Fig.1 shows the setup of the experiment. The position, on the optical axis, of both the lens aperture acousto-optic modulator with the rotation stage was unchanged throughout the investigation. A) Familiarisation with RF Driver Acousto-optic Modulator The Laser was switched on, as well as the RF driver, photo detector digital mulitmeter. The Bragg modulator rotational stage controls were familiarized with. The viewing screen was placed 50cm from the front of the acousto-optic modulator. The control of the RF Driver rotational stage were then altered the effects noted. B) Measurement of the Bragg angle The viewing screen from part A) was placed, so that the centre of the screen was at the centre of the zero order beam. The rotational stage was then rotated until the 1st order beams were both at their brightest. Each millimeter on the micrometer was found to be 1.69 ° change in angle. The number of squares was then measured from the right edge of the Zero order beam to the right edge of the right 1st order beam the right edge of the left 1st order beam. This gave the Bragg angle by using simple trigonometry. Then the answer was compared to the analytically found value. The following equation shows Sell’s law applied to the incident beam show how the light will be diffracted by the medium; Where Λ is the acoustic wavelength, ÃŽËœ is the angle from the conversion from the micrometer reading ÃŽ »/n the optical path length through the material, n being the Refractive index ÃŽ » being the wavelength of the laser light. The acoustic wavelength can be found by using the e lectronic frequency the speed of sound in the material, Lead Molybdate being 3750 m/s. Approximating for small angles, Equ.1 can be written as; Rafraction will occur at the crystal faces, allowing this gives the Bragg angle; .Where ÃŽ » was taken as 632.9nm laser light. Part C) Investigating the intensity of diffracted light with changing acousto-optic modulator angle The Photo detector was placed 50cm from the base of the modulator. It was aligned so the zero order maximum was entering the ‘Slow detector’ input the iris on the front of the photo detector was adjusted so that the full beam width could enter the detector no more. The slow detector output was then hooked up to the digital multimeter. The viewing screen was then placed to block infront of the acousto-optic modulator to block the laser light the multimeter reading was taken to give the ambient light or 0% reading. The laser light was then allowed to hit the photo detector, with no power applied from the RF drive to the modulator the reading was taken from the multimeter. This gave the full 100% intensity reading. The value of RF drive power that gave the minimum zero order reading was then found the RF power was then set at that value for the rest of the experiment. Th e modulator angle was set at 5.5mm the output power was recorded. Steps of 0.05mm were then taken the output power at each value was recorded. This was then repeated with the right first order beam, with the same start point increments. The values on the micrometer were then converted to angles in degrees the output power values were converted to percentages of the zero order maximum value. The Acoustic Intensity was then found using the equation; Where, Iac is the acoustic intensity, ÃŽ » is the laser light wavelength (632.8nm), L is the beam width (approximately 15mm) Pdif Pinc are the light power diffracted incident light power respectively. D) The Apparatus remained in the same setup as before. The Transistor-Transistor-Logic Gate (TTL) was then turned on. A square wave with an initial frequency was set. This causes the power into the RF driver to alternate between the manually set option on the knob completely off has a rise fall time of 50ns. The modulator was set to maximize the 1st order beam the angle was set to 5mm on the micrometer (8.45 °). The photo detector (still 50cm from the base of the modulator) was connected to the oscilloscope. The input from the TTL was also connected to the oscilloscope the signal from both the input TTL photo detector were shown. The photo detector was 1st placed in alignment with e zero order wave the result was recorded. The photo detector was then placed on the right hand side 1s order beam the resulting signals were recorded. The frequency was then increased to find at what value the signal was still modulated. Results Part A)It was found that increasing the RF drive power caused 1st order beams to appear a futher increase caused 2nd order beams to appear. Rotating the platform, from no rotation, 0mm on the micrometer, caused the 2nd order beam to dim disappear on the left hand side of the zero order maxima. The 1st order on the left hand side became brighter, then dimmed as the micrometer reading was increased. The zero order beam started dim, but as the micrometer reading was increased the acousto-optic modulator on the rotational stage became orthogonal to the viewing screen the beam became brighter. As the acousto-optic modulator moved past being orthogonal, the zero order dimmed the 1st order beam on the right hand side became brighter the 2nd order beam on the right hand side appeared. Part B) The angle between the right hand 1st order the zero order beam was found to be 0.0260 Rad  ± 0.009 Rad. The left hand 1st order beam was found to have 0.0280 Rad  ± 0.009 Rad angle between its elf the zero order beam. The theoretical Bragg angle was found to be 0.0118 Rad, taking the the spped sound in Lead Molybdate to be 3750 the electrical frequency to be 140MHz. Part C) Fig.2 shows the results for the part of the experiment Using the graph Equ.5, the Acoustic intensity was found to be 14.3 x 104 W m-2  ± 2.9 x 104 W m-2. Part D) the following figure shows the results from the zero order beam 1st order beam against the TTL input signal; Fig.3 shows the signal from the photo detector on channel 1, with the TTL square wave on channel 2. This figure shows the waves are in phase (the larger wave being from the TTL, the slightly hazier signal being from the photo detector) Fig.4 shows the signal from the photo detector on channel 1 again the TTL signal is on channel 2, showing this time the signals are out of phase. The delay between the zero order beam beam the TTL signal fluctuating between the zero 1 state was found to be 140nS  ± 10nS. As the pulse generator frequency was increased the beam was found to change to not resemble the TTL input signal. The maximum value where the beam was still modulated was found to be 110MHz  ± 10MHz. Discussion The experiments in this investigation were relatively easy to set up after some familiarsation took place. The control on the RF driver was a knob that had no indication of what magnitude the dial was set at, so it was difficult to identify if the setting had changed during readings being taken. In part A) it was fairly difficult to establish the edge of the zero order 1st order beams on the viewing screen. The laser itself was found not to give a stable reading, which made parts C) D) difficult. The reading from the laser on the multimeter fluctuated by roughly 10mV for each reading taken in part C). A larger amount of error was introduced by the instability of the laser, however if the investigation was to be repeated more measurements could be taken averages for values would give a clearer relationship. When the RF driver power was set to give the minimum zero order value, the 2nd order maxima were not visible. They gave readings witch fluctuated to the 0% reading or reading fo r the ambient light. This meant only the 1st order maxima could be investigated. Experimental judgments throughout this investigation cause error. Conclusion Through analysis, the angle at which the light diverged from the zero order maxima should be 0.012 Rad. It was found on this experiment that the first order maxima diverged from the acoustically modulated crystal at an angle of 0.027 Rad  ± 0.009 Rad. Through further investigation the 1st order maxima was found to be Ï€ Rad out of phase with the zero order beam. The acoustic intensity in experienced in the crystal was found to be 14 x 104 W m-2  ± 2.9 x 104 W m-2. References Leon Brillouin,Ann. Phys.(Paris) 17, 88 (1922). John M. Cowley (1975)Diffraction physics(North-Holland, Amsterdam)ISBN 0-444-10791-6 H. Eklund, A. Roos, S. T. Eng. Rotation of laser beam polarization in acousto-optic devices.Optical and Quantum Electronics. 1975;7(2):73–79.doi:10.1007/BF00631587 R.Y.Chiao, C.H.Townes and B.P.Stoicheff, Stimulated Brillouin scattering and coherent generation of intense hypersonic waves,Phys. Rev. Lett.,12, 592 (1964) Carl. R. Nave.Braggs Law. HyperPhysics, Georgia State University. Retrieved 2008-07-19 Bragg, W.L. (1913). The Diffraction of Short Electromagnetic Waves by a Crystal.Proceedings of the Cambridge Philosophical Society17: 43–57. F.L. Liu, P.St.J. Russell, L.Dong, Acousto-optic modulator using a fibre Bragg Grating, Optoelectronics Res. Cen., University of Southampton G. A. Coquin, D. A. Pinnow, A. W. Warner, Physical Properties of Lead Molybdate Relevant to Acousto-Optic Device Applications, J. App. Phy. A 6, Vol 42 (May 1971) A.Rosencwaig, A. Gersho, Theory of the Photoacoustic Effect with Solids, Journal of Applied Physics, 47(1), 64-69 (1976) A. Yarvin, P. Yen, â€Å"Wave Propagation in Periodic Media† in Optical electronics in modern communication, (Oxford 2007), pp. 539-82

What Are the Main Problems Associated with Using Plastic Bags?

Module code: FC 5012T Title: Skills for Study 1 Assignment question: What are the main problems associated with using plastic bags? Identify solutions to reduce these problems. Word count: 742 Tutor name: Bird, Marianne City University Number: 110065767 Submission Date: 26/10/2011 Plastic bags have been used on a daily basis since 1977 (Williamson, 2003) as a means of carrying items such as groceries as they are not only convenient but also cheap. However, the over-use of plastic bags has posed significant threats to the environment in recent times as they are non-biodegradable and also a threat to wildlife.The primary reason for this concern is that plastics bags are not re-used, but simply disposed of in landfills. These problems have both social and environmental impacts that are of global concern. This essay will begin by illustrating the problems associated with plastic bags, followed by the various ways in which society can hope to resolve this dilemma. The manufacturing proces s of plastic bags commences with the extraction of and handling of raw materials.Large amounts of energy are required to extract crude oil, and most of the electricity used in the process of manufacturing the plastic used in these bags comes from coal-fired power plants (Greenfeet, 2004). The fundamental components of manufacturing plastic bags are petroleum and natural gases (Lajeunesse, 2004), whereby 4% of the world’s total oil production is used in the production of plastic bags (Greenfeet 2004). The toxic emissions and consequently air pollution of chemicals and carbon dioxide during the production of plastic bags presents a serious concern for the environment.According to the Institute for Lifecycle Environmental Assessment (1990), the manufacturing of two plastic bags produces 1. 1 kg of atmospheric pollution, which contributes to acid rain and smog. Plastic bags are normally shipped to different consumer countries which also in turn has a harmful impact on to the envi ronment due to excessive emissions of pollutants such as sulphur (Long and Wagner, 2000). Each year there is an increase in demands for plastic bags, and therefore more are shipped, creating further environmental pollution concerns.This increase in demand has lead to the phenomenal upsurge in the use and misuse of plastic bags globally, both in developed and developing countries. Statistics show that 4 to 5 trillion plastic bags are produced per annum, whereby North America and Western Europe account for nearly 80% (Geographical, 2005; Reusable Bags, 2005). Cheeseman (2007) states that approximately â€Å"380 billion plastic shopping bags are used in the United States annually†; in turn, only 0. 6% of this is recycled. Almost 96% of plastic bags are disposed of in landfills (Williamson, 2003).This leads up to another problem as plastic bags are non-biodegradable – in other words, plastic bags do not biodegrade for over a thousand years (Stevens 2001). Plastic bags may also land in farms and in oceans which have an impact on the wildlife. Livestock such as cows may eat plastic bags while grazing. These pose a threat if ingested as they may tangle in their stomachs, causing serious injuries and potentially death (Dreyer et al, 1999; Rasmussen 1999). Each year over a billion birds and mammals die due to the ingestion of plastic bags (Baker, 2002).Many of these issues however, can be addressed and even resolved in several ways. Nowadays, a number of countries have begun to impose taxes on plastic bag consumption, with few even banning the use of plastic bags altogether. In Ireland a 15% tax has now been levied on the consumption of plastic bags, which has resulted in a 90% fall in plastic bag consumption. Many Asian and African countries, including China have also issued new policies on the banning of plastic bags (Ganster 2010 and Hill 2010). Some countries are now making new, more environmentally-friendly paper bags.These bags are biodegradable whi ch means will be able to biodegrade significantly faster compared to regular plastic bags. In Uganda, bags are now made out of banana leaves, making them more eco-friendly and are in themselves biodegradable (Hill 2010). Countries such as the USA have now begun implementing recycling programmes. However, its success has been limited as such services are not yet widely available (McKinney and Schoch, 2003) and the plastic used in the production of these bags are not easily recyclable. In conclusion, the problems presented by such plastic bags lie throughout he production line: from the production process to the way in which plastic bags are overly consumed, through to the ways in which they are disposed of. Although several solutions have been implemented to mitigate the issues caused by plastic bags, there is still much to be done to reduce future, drastic consequences to both society and ultimately the environment. Marquita K. Hill (2010). Understanding environmental pollution  . 3rd ed. United Kingdom: Cambridge university press. p345-346. Linda A. Mooney/ David Knox/ Caroline Schacht (2010). Understanding social problems. th ed. United states of America: Linda Schreiber-Ganster. p485. Hansard (2007), â€Å"Parliamentary Debates â€Å",  Kenya National Assembly Official Record,  Jul 25, pp. 15-17. Baker, R. 2002. â€Å"Ministerial Brief: Plastic Bag Levy. † Website. Accessed October 22,2011. http://sres. anu. edu. au/people/richard_baker/examples/briefing/minty/Minty. html Geographical. 2005. â€Å"Waste: An Overview. † Geographical 77(9): 34-35. Greenfeet. 2004. â€Å"Paper vs. Plastic – The Shopping Bag Debate. † Website. Accessed November 20, 2005. http://www. greenfeet. net/newsletter/debate. shtmlLajeunesse, S. 2004. â€Å"Plastic Bags. † Chemical and Engineering News 82(38): 51. McKinney, M. L. , and R. N. Schoch. 2003. Environmental Science: Systems and Solutions. Mississauga, ON: Jones and Bartlett Publisher s. Reusable Bags. 2005. â€Å"Facts and figures regarding the true cost of plastic bags. † Website. Accessed October 25, 2011. http://www. reusablebags. com/facts. php Long, R. , and M. Wagner. 2000. â€Å"Report Finds Ships the Dirtiest Transportation Source, Causing Smog at Sea and in Port: Lawsuit Filed Against EPA for Failure to Regulate Large Ship Emissions. Website. Accessed November 28, 2005. http://www. commondreams. org/news2000/0717-07. htm Reusable Bags. 2005. â€Å"Facts and figures regarding the true cost of plastic bags. † Website. Accessed November 27, 2005. http://www. reusablebags. com/facts. php Stevens, E. 2001. Green Plastics: An Introduction to the New Science of Biodegradable Plastics. Princeton, NJ: Princeton University Press. Williamson, L. J. 2003. â€Å"It’s Not My Bag, Baby! † On Earth: Environmental Politics People 25(2) (June): 32-34.

History of Film - 6962 Words

Plays and dances had elements common to films- scripts, sets, lighting, costumes, production, direction, actors, audiences, storyboards, and scores. They preceded film by thousands of years. Much terminology later used in film theory and criticism applied, such as mise en scà ¨ne. Moving visual images and sounds were not recorded for replaying as in film. The camera obscura was pioneered by Alhazen in his Book of Optics (1021),[2][3][4] and was later perfected near the year 1600 by Giambattista della Porta. Light is inverted through a small hole or lens from outside, and projected onto a surface or screen, creating a projected moving image, indistinguishable from a projected high quality film to an audience, but it is not preserved in a†¦show more content†¦[7] After this date, the Edison company developed its own form of projector, as did various other inventors. Some of these used different film widths and projection speeds, but after a few years the 35-mm wide Edison film, and the 16-frames-per-second projection speed of the Lumià ¨re Cinà ©matographe became standard. The other important American competitor was the American Mutoscope Biograph Company, which used a new camera designed by Dickson after he left the Edison company. [8] At the Chicago 1893 World s Columbian Exposition, Muybridge gave a series of lectures on the Science of Animal Locomotion in the Zoopraxographical Hall, built specially for that purpose in the Midway Plaisance arm of the exposition. He used his zoopraxiscope to show his moving pictures to a paying public, making the Hall the very first commercial movie theater.[5] William Kennedy Laurie Dickson, chief engineer with the Edison Laboratories, is credited with the invention of a practicable form of a celluloid strip containing a sequence of images, the basis of a method of photographing and projecting moving images.[citation needed] Celluloid blocks were thinly sliced, then removed with heated pressure plates. After this, they were coated with a photosensitive gelatin emulsion.[citation needed] In 1893 at the Chicago World s Fair, Thomas Edison introduced to the public two pioneering inventions based on this innovation; the Kinetograph -Show MoreRelatedBlockbuster History Films Essay1650 Words   |  7 PagesHistory films have often been criticised by academics and journalists as inaccurate depictions of the past. Yet there is no denying the fact that blockbuster history films are increasingly influential in shaping our understanding of historical people and events thanks to the accessibility of the medium. Producers of these films often take lib erties with facts to tell a more dramatic, engaging and entertaining story. They have a basis in truth but are greatly influenced by the writers’ and directors’Read MoreHistory And History Of The Arab Films1993 Words   |  8 PagesDo you think history is important? Why is it significant? And, does knowing the history of everything in the life matter? Actually, these questions and many other questions have been asked over many years all over the world and they have many different answers. Knowing the history of many different things in the life is very important because of one sufficient and helpful reason; knowing the history helps in understanding the present and in building the future. There are a lot of subjects and thingsRead More The History of Film Essay1286 Words   |  6 PagesA major change that has occurred in the development of film is the linearity of narrative. The history of film spans over one hundred years ago, with classical narrative emerging in Ho llywood around the nineteen thirties. The classical narrative period had a strong emphasis on linearity and coherence, where characters where goal centred and consistent in personality and action. In the nineteen sixties a change began to emerge in Hollywood, with Breathless (Jean-Luc Godard, 1960) breaking the editingRead MoreThe History of Film Editing1382 Words   |  5 Pagesa movie from this year compared to a movie from the 1930s, you would notice many differences. In the beginning, there was no digital technology to edit films. There have also been important contributors to help evolvement in film editing. In the process of editing film, there are some common editing techniques that have been used ever since film started. The way you edit a scene can also affect the mood and feeling of it. Although the editing of filmmaking has changed a lot over time, there are manyRead MoreThe History of Film, and the Film Industry Today Essay783 Words   |  4 Pagesfirst film capturing camera was called the â€Å"zoopraxiscope† or the â€Å"Wheel of Life.† Later on, in the 1890’s people began creating their own versions of portable cameras, whereas Lincoln’s camera was always mounted to a tripod, to prevent moving pieces from breaking. There is no way they could have known what an impact they would have had on the world. Film throughout the ages has created many incredible people, styles, and technology. Through film, there was less pressure for actors. Film directorsRead MoreThe History Of Film Gear1005 Words   |  5 Pages2017 could be considered the year of Film Gear. We had a lot of cool new gadgets, tools, cameras and more that arrive that filmmakers could fill their toolbox with. Here are ten of our favorites. 10. Storyclock Notebook - Born out of an idea by filmmaker Seth Worley, this new system for developing your ideas works on the premise of how an idea flows as time passes. Using the simple visual method of a clock, the Storyclock notebook turns your ideas into a viable cinematic story. For writers who struggleRead MoreSex Scene On Film History1699 Words   |  7 Pagessexual scene on film history Javaad Tare L4 Film production History and Culture 2500 word January 2017 Abstract Those are probably the questions or wonderings that surrounds almost ever teen s day life, and also at least 90% people outside the Movie Business and Industry who just watch Movies.(not pornography) So How are sex scenes in movies shot? As an actor/actress, how is the experience? When the sexual scene added to the films? What the propose of using adult nature on films? Those questionRead MoreThe History of Film Noir Essay1018 Words   |  5 PagesThe History of Film Noir Film Noir literally means ‘Black Film’. This term was first coined by French film critic Nino Frank, who noticed a trend in the darkness of themes in many American films that constituted wartime cinema. Classic film noir developed during the 1940’s during and after World War two, taking advantage of the post war zeitgeist of anxiety, pessimism and suspicion. Mistrust, fear, paranoia, and bleakness is obvious in noir, it reflects the cold warRead MoreA Brief History of the Film Industry1268 Words   |  5 PagesFilm industry is a group of factors that lead to moviemaking. The first idea of film was a picture, moreover pictures that moving in a certain way to look like a movie. The French Lumiere Brothers are the first hand of making the new modern film industry. In the beginning the films were with no technology, its lack of sound and colors, and it’s only for seconds. Then in the beginning of 1900c the narratives came to the movies and it developed to be recorded onto plastic film and shown by a movieRead MoreWatermelon Woman Analysis754 Words   |  4 Pages As having a historical aspect to novels and films can have an important impact on plots, one must look at the various ways history and historicity can be used. Both the novel Kindred and the film Watermelon Woman utilize these historical aspects in similar and opposing ways to tell their stories. With matters suc h as the knowledge (and/or lack of knowledge) and creating a imagine of history, the stories of Dana and Cheryl provide readers with a look at the variety of impacts that can affect them

The Debate Over The Minimum Wage Debate - 1737 Words

Andrew Carnegie once said â€Å"Do your duty and a little more and the future will take care of itself.† Carnegie: for better or worse, played an important part in the worker’s rights movement. Some of the very first movements for workers to unionize and protect their jobs came during Carnegie’s time and would mark the very beginning of long and difficult process to achieve worker’s rights that still continue to this day. The minimum wage debate is without a doubt part of these negotiations and has taken the spotlight in recent years. There are two sides to the minimum wage debate: the employees fighting for higher wages who would like to earn enough to keep food on the table for their family, and the employer who is doing what they can to keep†¦show more content†¦These sweatshops employed women and children and paid them far less than a reasonable wage. The minimum wage was created to â€Å"help individuals or families achieve self-sufficiency, and, as a result, coverage of minimum wage laws was extended to men and to workers in most low-paid occupations,† (Neumark Wascher, 2008). Throughout history minimum wage laws have been thought of as the right thing to do, but it is still uncertain if it is the correct way to achieve goals. Although the minimum wage debate had been going on for some time the very first federal wage law was passed in 1938 by Congress as part of the Fair Labor Standards Act. Moving forward, the next big event in the history of the minimum wage debate occurred in 1981 with the Minimum Wage Study Commission. This covered what was thought to be everything we as a country needed to know about minimum wage. Although some believed that there was still more to be known and in the mid-1990s, where it was found that â€Å"Minimum wages play an important role in youth labor markets†¦[and] the principal intent of the minimum wage [is] helping raise incomes of low-income families,† (Neumark W ascher, 2008). For the most part, that is still where the debate lingers today, whether raising the minimum wage is the correct way of helping people live on reasonable salaries and what that means for young people working low-income jobs. Many people that are against raising the minimum