...Final examination Theory 1. Explain the dispersion of light by a transparent dielectric material. The phenomen of dispersion is connected to the fact that the refractive index is dependent on the wavelength. Due to dispersion, the light waves from a complex radiation are bent by different angles as they enter a dispersive medium and they may be visualized separately. The index of refraction of a transparent dielectric medium is defined as the ratio of the speed of an electromagnetic wave in empty space to its speed in the medium. . It is a measure of the slowing factor for light traveling in that medium The refractive index can be expressed as a function of the electric and magnetic properties of the medium . For most of the materials that are transparent to visible light and . Hence the magnetic properties have a small effect on the light propagation. When an electromagnetic wave is incident on a medium, it electrically polarizes the molecules. This changes the value of which in its turn, determines the index of refraction. The process is wavelength dependent: different wavelengths will induce different polarizations of the molecules and, as a result, and will be different. So, the index of refraction changes with wavelength: The phenomenon described above is known as the dispersion of light. Equation is the dispersion relation. For most of the materials, decreases with the wavelength (see figure1). This phenomenon is known as normal dispersion...
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...400 nm to 700nm, this is called the visible spectrum, which is part of the electromagnetic spectrum. The largest of the visible spectrum is red which is about 700 nm and the smallest wave is violet which is approximate 400 nm. From figure 1 it can be seen the colours of light being separated by a triangular prism the longer waves (red) and shorter waves (blue) being separated. Diffraction, when waves meet a gap in a barrier they carry on through the gap, the waves spread out to wide extent into the area beyond the gap, as can be seen in figure 2. But the extent on how it does spread depends on the size of the gap, the larger the gap the less spreading which is done by the wave, the smaller the gap the more spreading the waves does. This exact phenomenon is the reason you can hear someone round the corner of a building before you see them or while driving your car you can still receive a radio signal miles away from the transmitter. Figure 2 Figure 2 When light passes through a small slit it can be seen pattern starts to emerge with a bright central region, and alternating light and dark bands. If the light is the same colour throughout the bands will be of the same colour. Red light has a broader pattern than blue light, suggesting that the diffraction effect increases with wave length. If we use white light, the...
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... the spectral pattern reflects a star’s composition. All stars are 95% hydrogen, so the variations in composition expose its age, luminosity, and origin. Composition of ages can be determined by observing the light of a star. The temperature of a star can be determined from its color and its spectrum. All stars have different colors because of its light radiation. Another way to determine the temperature of a star is to examine the spectral lines in the starlight. “Because we sometimes describe light as an electromagnetic wave, the complete spectrum of light is usually called the electromagnetic spectrum” (Bennett, Donahue, Schneider, and Voit, 2009). This is used to explain all types of electromagnetic energy that exist throughout the universe. Spectra consist of three different types: continuous, emission line, and absorption. Emission and absorption lines tells us that each type of atom, ion, or molecules obtain a rare set of energy levels. Every atom has its own rare spectral fingerprint because it has its own rare set of energy levels. If matter is made of hydrogen,...
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...Physics PHYSICS FORMULAE AND PRINCIPLES Fundamental quantities and SI units The standard units were set up by the international system of units, SI The fundamental quantities, there symbols and there SI units a listed below Quantity symbol SI unit & unit symbol Length l metre (m) Mass m kilogram (k g) Time t second (s) Temperature T Kelvin (k) Current I Ampere (A) Amt. substance mol mole 6.02 x 10 23 (molecules) Luminous intensity - candela (c d) MULTIPLES AND SUBMULTIPLES Multiples are larger than the base units and submultiples are smaller than the base units Multiples Symbol Prefix Meaning Example Deca d 10 1 0 Decameter Hecto h 102 100 Hectometer ...
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...Matter is also a general term for the substance of which all observable physical objects consist Properties of Substances Physical (Properties and Changes) A physical property is one that is displayed without any change in composition. (Intensive or Extensive) 1. Intensive: A physical property that will be the same regardless of the amount of matter. density: m/v • color: The pigment or shade • conductivity: electricity to flow through the substance • malleability: if a substance can be flattened • luster: how shiny the substance looks 2. Extensive: A physical property that will change if the amount of matter changes. • mass: how much matter in the sample • volume: How much space the sample takes up • length: How long the sample is Physical Change Change in which the matter's physical appearance is altered, but composition remains unchanged. (Change in state of matter) • Three main states of matter are: Solid, Liquid, Gas o Solid is distinguished by a fixed structure. Its shape and volume do not change....
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...laboratory, experimenting in the dark, he noticed that phosphor lights up when he switches on his cathode ray tube, dragging out electrons and accelerating them by a potential difference, the cathode ray tube is expected to be under vacuum, but there was just enough rest gas (air) that electrons got slowed down by being scattered by the molecules, today we know: when electrons are slowed down they radiate off their lost in kinetic energy – and that is X-rays an electromagnetic wave + a stream of high energy photons traveling at the speed of light at the time nobody knows how the radiation originates and of what kind it was: wave or particles? Röntgen could in a long series of experiments showed: - X-rays penetrate all substances to some extend, elements of low atomic weight are especially transparent, elements of high atomic number can bye used as shields for protection against X-rays - X-rays cause many substances to fluoresce, i.e. absorbing them and radiating off electron-magnetic waves of a different wavelength - X-rays are...
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...because they did not observe E) parallaxes for the stars. ----------- 14. Sunspots were discovered by C) Galileo. ----------- 15. Aristarchus argues E) for a heliocentric universe. ----------- 16. The higher the frequency of light B) the shorter (smaller) its wavelength. ----------- 17. Aristarchus estimated the relative distances to the Sun and Moon by observing the A) angle between the half Moon and the Sun in the sky. ----------- 18. The smaller the wavelength of light A) the larger its frequency. ----------- 19. The difference in the lengths of shadows simultaneously cast by identical sticks placed vertically in the ground at two different points on a meridian indicates that D) the Earth is not flat. ----------- 20. The spectral lines of a star are observed to be shifted toward larger wavelengths. This shows that E) the star is receding from us. ----------- 21. In order to account for the retrograde motion of the planets, Ptolemy introduced the A) epicycle. ----------- 22. The spectral lines of a star are...
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...was because it had a force acted upon it. This force was gravity. This force is absent in space so a body will continue its path unless it hits into something. When an object is stopped abruptly the higher the speed the body was moving at the bigger the force impacted on the body that it hit. This is why it would hurt when you catch a sliothar and your hand is completely stagnant. Some day to day examples of inertia are: • Being pushed back into your seat when an airplane takes off • Being jerked forward when your car suddenly stops • The “tablecloth trick” yanking a table cloth while the dishes remain in place. Electromagnetic spectrum The electromagnetic spectrum is a way of organising all electromagnetic waves according to frequency and wavelength. There are many frequencies such as Radio, Micro, Terahertz, Infrared, Visible, Ultraviolet, X-ray and Gamma. The frequency that is most important to human beings in the electromagnetic spectrum is light. The range that light can be seen is a narrow portion of the spectrum, from 0.4 microns (blue) to...
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...Module 02. Physics 1. Matter. Question Number. 1. An atom with 3 free electrons in its outer shell is said to be. Option A. pentavalent. Option B. covalent. Option C. trivalent. Correct Answer is. trivalent. Explanation. Number of electrons in the outer shell is called the valency - 1 = monovalent, 2 = divalent, 3 = trivalent etc. Question Number. 2. What is the mass number of an element?. Option A. Number of electrons and protons. Option B. Number of neutrons and protons. Option C. Number of electrons and neutrons. Correct Answer is. Number of neutrons and protons. Explanation. NIL. Question Number. 3. What do you get when you add 2H2 and O?. Option A. H2 O. Option B. 2H2 O. Option C. 2H2 O2 . Correct Answer is. 2H2 O. Explanation. Water is molecules each made up of 2 hydrogen atoms and 1 oxygen atom. Here ther is 4 hydrogen atoms, and 2 oxygen atoms, so we can make 2 water molecules. Question Number. 4. The splitting of a chemical compound is called. Option A. bombardment. Option B. synthesis. Option C. analysis. Correct Answer is. analysis. Explanation. NIL. Question Number. 5. What is the atomic number of an element?. Option A. The number of neutrons in the atom. Option B. The number of electrons in the atom. Option C. The number of protons in the atom. Correct Answer is. The number of protons in the atom. Explanation. NIL. http://en.wikipedia.org/wiki/Atomic_number Question Number. 6. An atom with 5 free electrons is said to be. Option A. pentavalet. Option B. covalent...
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...red, blue | Helium | Blue(2), green(2), orange(1), red(1) | Yellow, purple | Nitrogen | ROYGBIV (all colours) | | Nitrogen had the most spectra lines. The electromagnetic spectrum consists of all the different wavelengths of electromagnetic radiation, including light, radio waves, and X-rays. The Bohr-model would help us to determine which had the most spectra lines and colours because the colour of the lights is related to the lights energy. Light is absorbed when electrons jump down or up from one energy level to another, adding energy to an electron will cause it to get excited and move out to a higher energy level-the more energy that you add to the atom, the farther the electron will go. Bohr Rutherford’s experiments from that past have stated that electrons would be able to absorb and later release energy through colours of light. When this energy that comes out of the atoms falls towards the nucleus it releases energy in the process, this energy that falls towards the nucleus appears as light. Permitted energy levels are unique to all elements and this is what determines the range of jumping up and down from energy levels when an atom gets excited, and this is the same for all atoms of the specific element. For this reason it allows us to recognize elements from each other by using atomic spectra. How could this technology be used in astronomy? This technology could be used in astronomy to determine what different kinds of...
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...SALT pH- power of HYDROGEN in water Measurement: 0-6 ACID 7 SALT or NEUTRAL 8-14 BASE ACID- a substance that breaks into (H+) ION in an water WEAK: * Citric * Ethanoic * Carbonic * Acetic * Phosphoric * Nitrous STRONG: * Hydrochloric * Sulphuric * Nitric * Hydrodic BASE- a substance that breaks into (OH- (HYDROYYL) ION in water WEAK: * Potassium Carbonate * Sodium Carbonate * Ammonium STRONG: * Hydroxide Sodium * Phosphate Barium * Hydroxide Calcium * Hydroxide * Sodium ACID+BASE= SALT (NEUTRALIZATION) INDICATOR- a compound that will change color in the presence of an acid or base ANTHOCYANIN PIGMENT- natural indicator PERIODIC TABLE ATOM ATOM ATOM- building block of matter 1,000 ELEMENTS= 1,000,000 COMPOUNDS ELEMENT COMPOUND- more than one element in a mixture MIXTURE- combination of more than one material BIOLOGY BIOLOGY BIOLOGY- Bio (Life) -Logy (Study) BONTANY- Plants- FLORA ZOOLOGY-Animals-FAUNA...
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...HEAD | PREVIOUS | Chapter 1 Introduction 1.1 What is a Plasma? 1.1.1 An ionized gas A plasma is a gas in which an important fraction of the atoms is ionized, so that the electrons and ions are separately free. When does this ionization occur? When the temperature is hot enough. Balance between collisional ionization and recombination: | Figure 1.1: Ionization and Recombination Ionization has a threshold energy. Recombination has not but is much less probable. Threshold is ionization energy (13.6eV, H). χi | Figure 1.2: Ionization and radiative recombination rate coefficients for atomic hydrogen Integral over Maxwellian distribution gives rate coefficients (reaction rates). Because of the tail of the Maxwellian distribution, the ionization rate extends below T = χi. And in equilibrium, when | nionsnneutrals | = | < σi v >< σr v > | , | | (1.1) | the percentage of ions is large ( ∼ 100%) if electron temperature: Te >~χi/10. e.g. Hydrogen is ionized for Te >~1eV (11,600°k). At room temp r ionization is negligible. For dissociation and ionization balance figure see e.g. Delcroix Plasma Physics Wiley (1965) figure 1A.5, page 25. 1.1.2 Plasmas are Quasi-Neutral If a gas of electrons and ions (singly charged) has unequal numbers, there will be a net charge density, ρ. ρ = ne(−e) + ni(+e) = e (ni − ne) | | (1.2) | This will give rise to an electric field via ∇ . E= | ρϵ0 | = | eϵ0 | (ni − ne) | | (1.3) | Example:...
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...Bibliography 1. Introduction Spectroscopy Spectroscopy is the study of matter and its properties by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation. Spectroscopy may also be defined as the study of the interaction between light and matter. Historically, spectroscopy referred to a branch of science in which visible light was used for theoretical studies on the structure of matter and for qualitative and quantitative analyses. Recently, however, the definition has broadened as new techniques have been developed that utilize not only visible light, but many other forms of electromagnetic and non-electromagnetic radiation: microwaves, radiowaves, x-rays, electrons, phonons (sound waves) and others. Impedance spectroscopy is a study of frequency response in alternating current. Spectroscopy is often used in physical and analytical chemistry for the identification of substances through the spectrum emitted from them or absorbed in them. A device for recording a spectrum is a spectrometer. Spectroscopy can be classified according to the physical quantity which is measured or calculated or the measurement process. Spectroscopy is also heavily used in astronomy and remote sensing. Most large telescopes have spectrographs, which are used either to measure the chemical composition and physical properties of...
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...in antiquity with the Babylonians and with Hellenistic writers such as Archimedes and Ptolemy. Ancient philosophy, meanwhile – including what was called "physics" – focused on explaining nature through ideas such as Aristotle's four types of "cause". MAJOR FIELDS Branches of physics Physics deals with the combination of matter and energy. It also deals with a wide variety of systems, about which theories have been developed that are used by physicists. In general, theories are experimentally tested numerous times before they are accepted as correct as a description of Nature (within a certain domain of validity). For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger than atoms and moving at much less than the speed of light. These theories continue to be areas of active...
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...involved in it! The structure of hair Hair is made mostly of a protein called keratin, which is also present in nails. In hair, keratin molecules are arranged in straight bundles. These bundles are held together by disulphide bonds (-S-S-), which give strength to the hair. Disulphide bonds are made by the amino acid called cysteine. The cysteine of one keratin molecule forms a disulphide bond with the cysteine of the neighbouring keratin molecule. The more disulphide bonds there are in a strand of hair, the straighter it is. Ammonium thioglycolate: the perm salt Ammonium thioglycolate (HSCH2CO2NH4) is a compound that can break disulphide bonds. This is because it contains a thiol group (-SH). The thiol group replaces one of the sulphur atoms in the disulphide bond, like this: Keratin-S-S-keratin + 2HS-CH2CO2NH4 --> -HO2CH2CS-SCH2CO2H + 2NH3 + 2HS-keratin When the disulphide bond is broken, the keratin bundles come apart, and hair is weakened. Ammonium thioglycolate is therefore used widely in beauty parlours when customers want their hair re-styled. However, if you use too much of it, or if the reaction is left for too long, you could end up going bald. So do not, ever, try it at home! If you have watched the film Legally Blonde, you'll have seen Reese Witherspoon (acting as a law student) win her first case by her knowledge of the chemistry of perms! 1 How to get your hair re-styled If you'd like your hair curled, it's called a perm. If you like it straightened, that's rebonding...
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