Monday, January 27, 2020

History of Atomic Theory

History of Atomic Theory The atomic theory is developed since 2000 years ago the Greek philosopher Democritus proposed that there was a limit to how small one could be divide matter, this smallest matter indivisible particle was called atom. However this atomic theory of Democritus was criticized by Aristotle who proposed a model based on four basic elements of earth, air, fire and water. Aristotles view held for the next 2000 years as it better suited religious beliefs of the time. In 1801, an English teacher named John Dalton proposed his atomic theory which stated matter is composed of all small indivisible atoms, elements contain one type of atom; different elements contain different atoms, compounds contain more than one type of atom. In 1904, British physicist J.J Thomson and others demonstrated that cathode rays (electrons) were present in all matter. Thomson proposed that the atom was a sphere of positive charge in which embedded were rings of negative charges (electrons) , like plums in a pudding. Lather on, in 19 century, the discoveries of radiation leads to a new progress of Physics. We knew that certain elements emitting radiation, this suggested that atoms are no longer indivisible and not indestructible, as proposed in Daltons atomic model. Radiation provides an important tool for the study of matter. In 1911, Rutherford first suggested the use of alpha particles to probe the internal structure of the atom. Finally, the nucleus and its protons were discovered. Rutherfords scattering experiment Ernest Rutherford, directed an experiment to Hans Geiger and Ernest Marsden in 1909, in which the newly discovered alpha particles (Helium nuclei) were fired at a thin gold foil layer which only a few atom thick. At that time the atom was thought to be analogous plum pudding by Thomson with a negative charge (the plum) throughout the positive sphere (the pudding). Most of the alpha particle passed through with no or only very small deflections in a vacuum (see figure), as would been excepted on the Thomson model of the atom current at the time. About 1 in 8000 was deflected through angles greater than 90 degree. The result was so unexpected that Rutherford was very unexpected that Rutherford was promoted to write†¦.it was almost incredible as if you fired a 15 inch shell at a piece of tissue and it came back and hit you. Therefore Rutherford concluded that majority of the mass of the atom was concentrated in the nucleus. The small size of the nucleus explained the small number of the alpha particles that were repelled each other in this way. Rutherford showed that the size of the nucleus was less than about 10 -14m. Bohrs model, how it fit experimental observation Accelerated electrons emitted and lose energy which predicted by Predicted by Maxwell and confirmed by Hertz, however the electron doesnt spin into the nucleus because of energy losing. Later on, In 1903.H.G.J Morseley found simple, regular relationship between the frequencies of X-ray emission line, thus it provided an evidence to support Bohrs model. Scientist began to work on an alternating model to replace it. Bohrs postulates In 1913 the Danish physicist Niels Bohr (1885~1992), put forward some radical propositions to account for the discrepancies between Rutherfords model of the atom and the available experimental evidence. Bohrs postulates are 1. Electron can remove in certain allowed orbitsstationary states (energy) without radiating energy. 2.when an electron falls from a higher energy level to a lower energy level, it emits energy that is quantised by the plank relationship E2 E 1= hf. 3. Augular momentum (mvr) is quantised and can only take values of the nh / 2Ï€ when n is the principal quantum number. The first postulate account for the stability of the atom. However why the these stationary state excited was unknown. They exist was a fact. The second postulate explains the line emission spectra. Emission (or absorption) of Energy is discontinuous and corresponds to a transition between two stationary states. Since the energy can be quantized, the emission, the frequency of the emitted (or absorbed) radiation is predetermined. A transition between different states will lead to difference frequencies or colours. The third postulate effectively sets limits on the radius of the allowed orbits. Bohrs model Bohr realised that if his model was correct, each atom would have a spectral fingerprint to the differences between electron energy level in that atom. The Rydberg equation which also known as Balmer equation, has given him evidence for the quantised emission of the energy from hydrogen atom, leading him to going on to further his model and define his postulate. So the hydrogen spectrum was very significant to the development of Bohrs model of the atom, because without the understanding of it, Bohr may not continue his work of the model. Produced and observable when hydrogen gas was excited by the addition of energy. The equation in the original form was modified by Rhydberg until it worked and could be applied to explain the spectrum of hydrogen by using integer values of n, only as suggested by Bohr in his postulates. Quantum number and quantum changes Its possible to determine the energy of each orbit using Bohrs model and from this construct an energy level Figure for hydrogen. The figure below shows the energy these energy levels. Alternatively a transition between stationary states can be show in figure. B. The Balmer series of lines occurs when the electrons fall to the n=2 level from n=2 level n=3,4,5 and 6 levels. This is illustrated differently in figure. B. How Bohr describes the hydrogen spectra Bohrs model of the atom wad quite similar to that of Rutherfords with two important differences firstly, it assisted positions to the electrons, but secondly the electron energy level s were quantised. This was radically new, the idea that electrons had energy states and could absorb and emit energy to change states, and had no evidence. Bohr realised that if his model was correct, each atom would have a spectral fingerprint to the differences between electron energy level in that atom. The Rydberg equation provided him evidence for the quantised emission of the energy from hydrogen atom. It leads him to going on to further his model and defines his postulate. So the hydrogen spectrum was important to the development of Bohrs model of the atom. The energy levels describe by Bohr is clearly marked. According to Bohr, the Balmer series (shown on the bottom of the diagram as the hydrogen spectrum) was cause by changing energy levels, in the process releasing light. As shown, larger energy changes produce more energetic photons, as seen in Balmers series, as further, this diagram shows how the Balmer series is formed by successive electron transition to the 2ndshell (transition to other shell produce additional lines named after their discoveries.) This is a great achievement that the Bohr s model is able to provide a physical basis for the Balmer series formula. From his second postulate E f Ei= hf. (i) states for initial energy level (f)states for final energy level Ei=1/ni2E1and Ef=1/nf2E1 hence: hf =1/ nf2E1-1/ ni2E1=(1/ nf2-1/ ni2) E1 And since c=fA=>A=c/f the expression reduces to 1/A=E1/hcX(1/ nf2-1/ ni2) where R states for Rydbergs constant, RH(hydrogen)1.097X 107m-1. By using the mixture of classical physics and quantum physics, Bohr was able to define the equation for the spectral lines of hydrogen. He didnt know why the electrons obeyed his rules. These were purely empirical results. Problems with the model For all the success, the Bohr model of the atom had serious limitations: It and ad hoc mixture of classical and quantum physics; it allows some laws of the classical physics held and others did not. Hydrogen has only one electron, and Bohrs postulate are only able to explain it. It cant work fo r multi-electron atoms. It could not explain the relative intensities of the spectral line; some lines were more intense to the others and it was not known why this should occur. Certain spectral line were foun of a number of very fine and close lines and the cause of these hyperfine spectral lines could not be explained. The splitting of spectral lines when the sample was placed in a magnetic field (called the Zeeman effect, and discussed below) could also not be explained. The postulates faced a problem that it is suited for larger atom. Hydrogen is the simplest atom containing only one electron. Similarity He+and Li+have one electron. Bohrs model works with theses atom and ions. In all the other atoms however the electron interact with each other. In a larger atoms the outer electrons are shielded from the nucleus by the inner electrons. Interaction between electrons also result in different energy levels. The affect Bohrs model to the extent that the spectra of multiple electrons could not be explain. When the spectrum of the hydrogen was examined it was noted that the emission line varied in intensity. Some were quite intense and others were less intense; some were sharp and some were boarder. The following figure. illustrate these differences. Bohrs model could not explain these features but later it was explained that electron orbited in a ellipse and not in a circles. As the developing of the light spectroscopes improved it was found that some of the spectral lines were made up with hyperfine lines. This suggestion spitted Bohrs energy level theory; however there was no explanation for this. The Zeeman Effect Zeeman Effect occurred when a magnetic field us pass through a discharge tube. The magnetic field increased the hyperfine splitting of spectral lines, further breaking them up. As the limitation, Bohrs model was unable to explain the experimental evidence. In 1896 a Dutch physics Pieter Zeeman (1865-1943) found that when he placed a source of sodium light between the poles of a strong magnet the lines split into three or more. This could not explain by Bohrs model, The spectral line of some elements can even split to 15 lines. This is called the anomalous Zeeman effect. It cant be explain by that time, and it leads to the new developing of the model to explain it. This begin with the work of de Broglie. The following is the formal definition of Zeeman Effect: The splitting of single spectral lines of an emission or absorption spectrum of a substance into three or more components when the substance is placed in a magnetic field. The effect occurs when several electron orbits in the same shell, which normally have the same energy level, have different energies due to their different orientations in the magnetic field. A normal Zeeman Effectis observed when a spectral line of an atom splits into three lines under a magnetic field. Astronomers can use the Zeeman Effect to measure magnetic fields of stars. The following diagrams shows the normal spectral line and the Zeeman effect. References Textbooks 1. Excell HSC physics by Neville Warren published in 2007 2. Jacaranda Physics Second Edition published in 2004 3. Bohr and quantum theory by Paul Strathern in1998 4. Physics Spectrum by Peter H.Eastwell published by McGrathHill in 2000. Websites Ruthorford scattering experiment http://en.wikipedia.org/wiki/Rutherford_scattering last updated 19 July 2008 http://library.thinkquest.org/19662/high/eng/exp-rutherford.html Atomic structure discovered http://www.neoam.cc.ok.us/~rjones/Pages/online1014/chemistry/chapter_8/pages/atomic_structure_discover.html Figures Figure1.Demorcuris http://www.dl.ac.uk/TCS/Software/DL_POLY/ATTIC/DEMOCRITUS/Pictures/democritus.jpg Figure2. Aristotle http://www.bun.kyoto-u.ac.jp/phisci/Images/aristotle.jpg Figure3. John Dalton http://www.learner.org/channel/courses/essential/physicalsci/images/s4.dalton.jpg Figure4. J.J Thomsonhttp://www.wired.com/images/article/full/2008/04/jj_thompson_400px.jpg Figure5.Henri Becquerelhttp://www.mlahanas.de/Physics/Bios/images/HenriBecquerel.jpg Figure6. Ernest Rutherfordhttp://z.about.com/d/chemistry/1/0/n/T/rutherford1.jpg Figure7. Niels Bohrhttp://www.springtimepublishers.com/images/Niels_Bohr.jpg

Sunday, January 19, 2020

Persuasive Essay on John Proctor from the Crucible Essay

Who is John Proctor? Is he is a hero, a villain, a conqueror? Some may think he is craven, but others may credit him with great fortitude. This brave man was one of many who died for what he believed in. Although many people tried to persuade him to do otherwise, he stood his ground and died an innocent man. John had many reasons for choosing what he did. At first he was going to confess to save his life and be with his family. When Danforth made him sign the paper so he could post it on the Church doors, Proctor lost it. â€Å"It is my name! Because I cannot have another in my life! Because I lie and sign myself to lies! Because I am not worth the dust on the feet of them that hang! How may I live without my name? I have given you my soul; leave me my name!† is something he yelled to the court right after signing the paper. It was his name that they were taking away from him and it was the only one he will ever get. His sons will carry on that name, and if they post his it up for everyone to see, his good name will be ruined. Proctor is looking out for his sons, so they can carry on the family name with good reputation. Proctor had a right to not want his name up on the church doors. He didn’t want everybody seeing that he had confessed that he was a witch. John is supposed to be the guy everyone in the town looks up to. He didn’t want them seeing that he had committed a sin just so he could keep his life. He felt there was no need for them to use him to get other people to follow in his steps and lie. Proctor said to the court, â€Å" You will not use me! I am no Sarah Good or Tituba, I am John Proctor! You will not use me! It is no part of salvation that you should use me!† As a result of all this anger, John rips up the paper he signed. That being the case, John Proctor was hanged for the assumptions of being a witch. I know you all are outraged by the aftermath of all this, but Proctor made the right choice. He was concerned about having his â€Å"confession† made public. He was primarily afraid that his sons would never respect him and would think of him as craven fo r giving into the court. He died for the good of his family, not himself.

Saturday, January 11, 2020

Evolution of Human Speech Essay

It can not be disputed that speech is an important aspect in communication and above all it enables man to adapt to his environment by expressing his feelings, thoughts and sentiments. The power of the spoken word is also apparent in different authorities at it reflects what should be done and the ultimate success of the society. This illustrates why this art was adopted millions of years ago by the ancient man and has been used since then. However, the origin and development of speech is still unclear with various theories being put forward to address this issue. The most recent development in this field has been the proposal that this unique human characteristic developed from the gene FOXP2 in the KE family. However, this is yet to be affirmed as counter propositions have been raised, both by scientists, anthropologists and biologists. It is upon this background that this paper aims at analyzing the different phases of the evolution of human speech. Speech is a complex occurrence that is characterized by intonation and flow. However, Hewitt emphasizes that gestures are the most fundamental aspect of speech because of the fact that speech emanates from the movement of certain body organs in a systematic manner (342). From this, he further argues that the earliest human beings essentially used gestures in communication (342). This marked the earliest form and starts a journey to modern human speech. According to Crow, man definitely developed this sign language from the birds and the insect gestures (49). In this respect, he indicates that the birds usually take a material for nesting to the partner as a sign of proposal. In addition, the bees usually move their tails in a certain specific motion when they land on a flower that has nectar. From observing the characters of these and other animals like the dogs and the cats, man came up with a sign language to enable him communicate just like the other animals (Hewitt 342). As such different gestures were adopted by man to symbolize different things and ideas. For example, waving meant good bye, putting fingers on the lips meant keep quiet and shaking ones head meant disagreement. Hauser indicates that these gestures are still being used by the modern man and has the same implication (52). In addition, the gestures are universal and mean the same thing in diverse cultures. This has an implication that speech developed from a single source. Further, by watching the animals such as dogs and chimpanzees make some sounds when expressing different emotions, Maddeison points out that man also imitated them and came up with certain syllables that could convey the different emotions like for instance crying, laughing among others (56). Indeed, he affirms that the traditional man was able to grunt, cry and produce other emotional sounds with the help of his laryngeal glands. However, Hewitt argues that man developed speech because of his craftsmanship (342). To this end, he indicates that as man involved his hands in practical activities like Agriculture and crafts, he increasingly found it difficult to use his hands to communicate by gesturing while working at the same time. Furthermore, since his eyes also concentrated on the duties he was doing, it became difficult to see and acknowledge the gestures. According to Hewitt, this prompted him to derive other ways of expressing his ideas while working at the same time (342). Thus, Crow shows that he developed this using the lips and the tongue and that is when speech was born (57). Development of speech is thus related to the gestures that man once used. In this respect, it can be noted that children that are learning how to write often twist their tongues as their hands move. In addition, it can be observed that when a person is using a pair of scissors to cut anything, usually, the jaws of the person also move simultaneously. From this, Hewitt argues that it can be concluded that as it became more and more difficult to use hands in gesturing, man adopted the gestures using his jaw, lips and tongue (342). Hence, the development of speech is actually related to the activities that man engaged in. In other words, man adopted his speech from movement of his hands as he concentrated on different activities. With time, man got used to using the jaw, tongue and lips and his hands retired completely from gesturing. Afterwards another vital discovery was made that if air could be blown through the nose or mouth as the jaw, lips and the tongue moved systematically, these movements could become audible either as whispers or as sounds (Hauser p. 55). This reflected the sounds of grunting, snoring and crying made by man initially. As a result man was able to hear these sounds and hence communicate even when in the dark or when away from his peers, something he could not do earlier on. However, it was soon realized that not all movements of the jaws, lips and tongue were successful in producing these audible and coherent sounds. Hence, according to Hewitt, man decided to limit the mouth movement to up and down and not sideways (343). This was very effective in producing the coherent and audible sounds and man was then able to communicate effectively. Afterwards, man realized that the repetition of these sounds could make words and many words could make a speech. He made this idea practical while relatively using the words and finally, he was able to communicate clearly. In addition, Hauser argues that the development of these words was contributed to by the activities that man engaged in (57). For example, he explains that the word â€Å"sip† originates from the act is sipping. According to him, when man sips any liquid, and air is blown in to the mouth, the sounds of sip sap are produced. This explains how the word sipping came in to existence. It should be noted that these words are acknowledged ad appreciated universally and including in English. In the development of speech, Crow points out that man started with simple words and consonants before developing more complex words (62). To this effect, he indicates that the baboon can say certain simple words like man, is, eat amongst others although it can not use the words successively to make a sentence. Likewise, Crow contents that the development of speech took the same pattern (62). According to him, man started with simple words like go, eat, is amongst others before he came up with more complex words. However, unlike the baboon, man was able to repeat these sounds because he has two interlinked tubes in the vocal track while the baboon and the chimpanzee have only one (Crow p. 63). This explains while these animals, besides being hominids can not use speech. Words differ considerably because of the different environment and other scenarios that are unique to different areas. These include the climatic conditions, culture and other natural episodes and scenarios that characterize different areas. Despite this, Hewitt asserts that speech originated from the very first attempt by man to use lips, the tongue and jaws (343). This development is perceived to have occurred almost 400,000 years ago when is thought to have developed the essential organs to aid in the same. Specifically, the hypoglossal canal is perceived to be instrumental in attaining this condition and the right size for this is thought to have developed at this time. In addition, the gland is effective in transferring the relevant signals to the brain which then develops the ideas to be passed on. Despite the development of these vital organs, it is not clear whether speech developed concurrently or later on as other studies point out that speech developed only 100000 years ago (Maddeison, p. 62). To this effect, he argues that other vital features in speech development like the long neck developed almost 100000 years ago and therefore, speech developed then. Conclusion In conclusion, it can be ascertained that the development of speech in man is a phenomenon that started millions of years ago. This started by man imitating the gestures made by birds, insects and animals. Then, he started emulating the sounds made by the same and gradually developed his own sound system. It is also worth noting that the advent of craftsmanship contributed a great deal to the development of speech. In fact, it can be argued that this was the major factor that made man develop his speech. Works Cited Davidson, Hauser. Development of Speech in the Hominids; Cambridge: University Press, 1997. Foged, Maddeison. The Diversity in Linguistics; UK: Oxford, 1996. McLarnon, Hewitt. â€Å"Anthropology: The Origin and Development of Human Speech† American journal of Linguistic Inquiry, 109 (3) 1999: 341-343 Ploog, Crow,J. The Modern Man and Development of Speech; UK: Ox

Friday, January 3, 2020

The Partition onf India - 1231 Words

The Partition of India in August, 1947 was a significant event in history that accounted for the separation of one of the world’s oldest civilization into two, independent nations – Pakistan and India. Like many other wars in history, The Partition of India was instigated by religious, political and social conflict. This resulted in violence, discrimination and the largest human displacement in contemporary history. While the Partition was well-studied, much of our understanding was focused on the political side of history, not the human side of it. This was why oral history played an important role in manifesting the complexity of a historical event. Our focus here is Maya Rani’s testimony from Butalia’s book, The Other Side of Silence:†¦show more content†¦To Rani, ‘people dying here, others dying there’ (cited in Butalia, 2000, p.268) was something that happened every day, it was no surprise to her. Thus, Rani’s cynical view about the future of India and Pakistan was conceivably drawn from memories of witnessing horrendous fights and strife throughout her whole life (cited in Butalia, 2000, p.268). Official documents have little say about women and children of the Partition as they were viewed as a collective. Earlier reports on the abduction of women only gave the reader the statistics and brief statements that glorified community nationalism rather than the victims itself. Many failed to dwell into the individual trauma of this particular group (Menon Bhasin, 1998, p.11). Rani’s testimony was significant in that not only it opened us to another outlook from a witness point of view; it also revealed that people who were not physically involved were also affected psychologically. This was also the only part in the testimony where Rani displayed sympathy and grievance. Her sensitivity and deep connection with these victims correlated with age and gender. Her emphasis on the words ‘young’ and ‘girl’ throughout her testimony evoked our sense of disbelief that people would do such inhumane things to each other (cited in Butalia, 2000, p.271). Her hesitant manner, evident