Alberta Education Physics 30 Program of Studies Checklist PDF

 Program of Studies Checklist The following is a list of ideas and concepts you need to know to be able to pass the Unit A test. They are taken from the Alberta Education Program of Studies. Check off each idea as you study it at home General Outcome: describe the electrical nature...

 Program of Studies Checklist The following is a list of ideas and concepts you need to know to be able to pass the Unit A test. They are taken from the Alberta Education Program of Studies. Check off each idea as you study it at home General Outcome: describe the electrical nature of the atom Knowledge Outcomes: I can:  Describe matter as containing discrete positive and negative charges  Explain how the discovery of cathode rays contributed tot eh development of atomic models  Explain J. J. Thomson’s experiment and the significance of the results for both science and technology  Explain, qualitatively, the significance of the results of Rutherford’s scattering experiment  Explain, qualitatively, the significance of the results of Rutherford’s scattering experiment, in terms of scientific understanding of the relative size and mass of the nucleus and the atom Performing and Recording Outcomes: I can:  Perform an experiment or use simulations to determine the charge-to-mass ratio of the electron Analyzing and Interpreting Outcomes: I can:  Determine the mass of an electron/ion, given appropriate empirical data  Derive a formula for the charge-to-mass ratio that has input variables that can be measured in an experiment using electric and magnetic fields Communication and Teamwork: I can:  Select and use appropriate numeric, symbolic, graphical or linguistic modes of representation to communicate findings and conclusions [PHYSICS 30] 2 General Outcome: describe the quantization of energy in atoms and nuclei Knowledge Outcomes: I can:  Explain, qualitatively, how the emission of EMR by an accelerating charged particle invalidates the classical model of the atom  Describe that each element has a unique line spectrum  Explain, qualitatively, the characteristics of, and the conditions necessary to produce, continuous line-emission and line-absorption spectra  Explain, qualitatively, the concept of stationary states and how they explain the observed spectra of atoms and molecules  Calculate the energy difference between states, using the law of conservation of energy and the observed characteristics of an emitted photon Initiating and Planning Outcomes: I can:  Predict the conditions necessary to produce line-emission and line- absorption spectra  Predict the possible energy transitions in the hydrogen atom, using a labeled diagram showing energy levels General Outcome: describe nuclear fission and fusion as powerful energy sources in nature Knowledge Outcomes: I can:  Describe the nature and properties, including the biological effects, of alpha, beta, and gamma radiation  Write nuclear equations, using isotope notation, for alpha, beta-negative decays, including appropriate neutrino and antineutrino  Perform simple, non-logarithmic half-life calculations  Use the law of conservation of charge and mass number to predict the particles emitted by a nucleus  Compare and contrast the characteristics of fission and fusion reactions  Relate, qualitatively and quantitatively, the mass defect of the nucleus to the energy released in nuclear reactions using Einstein’s concept of mass- energy equivalence Initiating and Planning Outcomes: I can:  Predict the penetrating characteristics of decay products Analyzing and Interpreting Outcomes: I can:  Graph data from radioactive decay and estimate half life values  Interpret common nuclear decay chains [PHYSICS 30] 3   Graph data from radioactive decay and infer an exponential relationship between measured radioactivity and elapsted time  Compare the energy released in a nuclear reaction to the energy released in a chemical reaction, on the basis of energy per unit mass of reactants General Outcome: describe the ongoing development of models of the structure of matter Knowledge Outcomes: I can:  Explain how the analysis of particle tracks contributed to the discovery and identification of the characteristics of subatomic particles  Explain, qualitatively, in terms of the strong nuclear force, why high-energy particle accelerators are required to study subatomic particles  Describe the modern model of the proton and neutron as being composed of quarks  Compare and contrast the up quark, the down quark, the electron neutrino, and their antiparticles in terms of charge and energy (mass- energy)  Describe beta-positive and beta-negative decay, using first generation elementary fermions and the principles of charge conservation Initiating and Planning Outcomes: I can:  Predict the characteristics of elementary particles, from images of their tracks in a bubble chamber, within an external magnetic field Analyzing and Interpreting Outcomes: I can:  Analyze, qualitatively, particle tracks for subatomic particles other than protons, electrons and neutrons  Write beta positive and beta negative equations, identifying the elementary fermions involved.  Use hand rules to determine the nature of the charge on a particle  Use accepted scientific convention and express mass in terms of mega electron volts [PHYSICS 30] 4  Atomic Physics Vocabulary Update this list throughout the unit with new Physics vocabulary. Term Definition [PHYSICS 30] 5  Discovery of the Electron John Dalton Elements are made up of smaller objects called atoms Billiard ball model/solid sphere model Worked great to explain chemical reactions but not much else J. J. Thomson Used cathode ray tubes – he didn’t know that cathode rays were actually electrons 1st experiment To see if negative charges could be separated from the cathode rays using a magnetic field. When he failed to do this he concluded that cathode rays were negative charges. 2nd experiment To see if he could cause cathode rays to be deflected in an electric field Initial attempts failed as stray air molecules kept being ionized and messing up results Improved the vacuum tube and was able to show that this is the case 3rd experiment – the big one Allowed him to measure the properties of cathode rays. & Ore Combined with the work of others he was able to determine the charge to mass ratio of the electron Hot filament which ejects electrons, these electrons then travel between two parallel plates are accelerated as a result 2nd region containing a magnetic and electric field o If just the electric field is turned on, the electrons (according to the diagram) will travel upwards o If just the magnetic field is turned on, the electrons (according to the diagram) will travel downward. o If both fields are turned on, then (according to the diagram) the electrons will be undeflected and travel in a straight line [PHYSICS 30] 6  end of tube Thomson’s Setup / de t change - Thomson’s Raisin Bun/Plum Pudding Model changes - - - - --- Thomson concluded that atoms could be further broken down into positive and -- negative charges He believed that the positive charge was spread out over a region (the bun) and that smaller electrons (the raisins or plums) were embedded with this positive charge Thomson’s model was a big deal at the time because it was the first to suggest separate positive and negative charges. 1. You have just finished setting up a CRT like Thomson’s. Determine the velocity of the electrons if the magnetic field is 3.65 T and the electric field is 7.62 x 105 N/C. Explain the significance of your answer. B = 3 65T. Fe En= B 62x10SN/C GE) = - E = 7. This that is the electrons will speed = have Have = 208767 m/s if they through field the x05m/s) region undeflected. Gelocity selection) [PHYSICS 30] 7  2. You decide to try to recreate Thomson’s experiment. You set up your cathode ray tube with an electric field of 1.86 x 104 N/C between the plates and a magnetic field of 5.80 x 10-4 T. circle This setting result in electrons traveling straight through when they are both turned on. After shutting down the electric field, you measure the path of the electron. It has a radius - of 0.325 m. Determine the charge to mass ratio according to your experiment, and compare it to the accepted value. IE) with both = 1. 86 x10Y NIC fields on , velocity selection and we can 1 Bl occurs = 5 80 x 10- 4T. determine v the electron. of r = 0. 325m Fe Fm (IE) (415) = F = Fm a misna = = NON =G = 3 2009/107 Discovery of the Nucleus. = 1 70127. x10" Gug 10" = 1. 70 x C/kg Alpha Par cle alpha Is a helium nucleus -↳ 24 Hat & Represented as either _________________________ OR Released by some radioactive materials Rutherford Scatering Setup Place a radioactive sample that emits alpha particles inside a lead box with a hole Thin gold sheet in front of that o Gold can be made so thin it is only a few atoms thick Place a zinc coated looped screen on the other side. A glow is produced every time an alpha particle hits the screen [PHYSICS 30] 8  very thin e Zinc scrun of Rutherford’s Setup ~ surphide I - ↳ screen glows - where thit at - Lead Expected Based on Thomson’s model, which was accepted at the time: The positive charge of the atom the was spread out over entire atom. The effect of this positive charge would be very weak on other charges Negatives are irrelevant because they are so spaced out and tiny This would produce very small, if any scattering angles What Happened Small scattering angles were observed but some alpha particles scattered at very large angles Even more shocking was that a small number bounced straight back Rutherford described this by saying that it “Was almost as incredible as if you fired a 15- inch shell at a piece of tissue paper and it came back and hit you” The only model that could explain these observa ons was a concentra on of posi ve charge in the centre of the atom, a bunch of empty space and electrons in orbit The empty space and electrons in orbit meant that most alpha particles go straight through The concentration of positive charge in the centre would explain why some scattered at large angles or bounce straight back [PHYSICS 30] 9  - = Rutherford’s Planetary Model - # The nucleus is where all the positive charge is found - The electrons orbit the nucleus at random positions Still no mention of neutrons since they had not been discovered Serious Flaw Electrons would be orbiting in a circular pattern This means they are accelerating (since their direction is changing) Maxwell said that any accelerating charge had to be emitting energy This means electrons should be continuously losing energy This would result in electrons spiraling and crashing into nucleus This obviously doesn’t happen, so it was clear changes needed to be made The Bohr Model of the Atom Rutherford’s Planetary Model Model had its merits – positive nucleus, and electrons outside of that The electron orbits were a problem – Bohr examined this Discrete Energy Bohr proposed discrete energy levels Electrons couldn’t be in any old orbit because they continuously emit EMR and experiments showed that energy is only emitted at specific frequencies Inspiration for Bohr’s model came from spectroscopy – involves analyzing the spectrum produced by various sources after being passed through a diffraction grating [PHYSICS 30] 10 Con nuous Spectrum Passing white light through a spectroscope produces a rainbow. This is called a continuous spectrum because it contains all the colours of the rainbow and the colours blend into each other Produced by any object that emits white light right ROYGBIV Crainbow) white diffraction grating Light emited by gases made of single elements does not appear white. This is because elements only emit certain wavelengths of EMR As a result, the spectrum only contains certain wavelengths of light Each element has its own unique spectrum, that acts like a fingerprint for that element Emission Spectrum Light Occurs when we heat a gas at a low pressure Black background with bands of colour that correspond to the wavelengths of light being emitted. o These wavelengths correspond to energy level transitions within the atom sample ↑ contain element E faction "III I grating Absorp on Spectrum Centrale Occurs when white light passes through a cool, low pressure gas Continuous spectrum with dark bands of colour missing that correspond to the wavelengths of light that are being absorbed o These wavelengths correspond to energy level transitions within the atom ⑧ absoption spectrum sonight -low pressure [PHYSICS 30] gas 11 For a specific element, if you overlay the absorp on spectrum with its emission spectrum you will get a con nuous spectrum /Emission ~ 1 Dark-line Balmer Came up with an equation that showed that spectra being seen formed a clear pattern Bohr saw Balmer’s formula and was inspired since everything fit together well Only specific wavelengths of light were being emitted/absorbed o These wavelengths of light corresponded to electron transitions between energy levels o An electron moving from a higher energy level to a lower emission energy level emitted/released energy in the form of a photon with a specific wavelength. " o An electron moving from a lower energy level to a higher & absorption energy level absorbed energy in the form of a photon with a specific wavelength Bohr said that these energy levels are stable and the electrons in these levels do not emit EMR as they orbit o Since these electrons are not losing energy we sometimes refer to these positions as stationary states, it doesn’t mean that they are actually stationary, just that they are stable. [PHYSICS 30] 12 Energy Level Sizes and Energies Bohr calculated the radius of the lowest energy level in hydrogen (r1 = 5.29 x 10-11 m) and the energy associated with that energy (E1 = -2.18 x 10-18 J or -13.6 eV) o Bohr made the energy negative because you have to add energy to make a transition to a higher energy level. An electron that has been ionized (completely removed from the atom), has an energy of zero and an energy level number of infinity 1. Using the diagram determine the wavelength of light emitted when an electron moves from the fourth to the second level. Will a photon be absorbed or emitted? higher n to lowe n- > emit a photon te Al = * 1E = Ez Eq - # = = 4 89eV-7 93eV -. 3 04 eX. X = # KVS)1300o. ↑ ignore n = 4 14. x 10 Vs - 4 09x10 - 7 m. c 3 x108m/s -num =. 00 Violet 2. Using the energy level diagram for Hydrogen, determine which photon produced from the Lyman series has the longest wavelength and calculate the wavelength. C Y S large-smae 4) NU x ↑ 3 * 300 2 E, = 1 026 10 Em DE : Es x -. 6 -1 Sev) 103 = 13 = >. nm. = -12 /ev -. ignor = 4 14. x 10Vs I X C= 3. 00 x 108 m/S [PHYSICS 30] 13  The Quantum Model Bohr’s Model Was a great triumph, but it also had several problems that even Bohr recognized o Why shouldn’t electrons emit EMR when they are in their stable energy levels? o The formula that Balmer originally developed only worked for hydrogen o It was found that each emission line is actually made of two or more closely spaced lines, called the fine structure 1 o Some emission lines are brighter than others t Par cle vs Wave Bohr’s electron was still just a particle De Broglie later showed that particles have wave like properties It started to become clear that electrons cannot be thought of as particles only, but they exhibited wave properties as well Assume that you figure out the de Broglie wavelength of an electron For the electron to orbit the nucleus, its wavelength must be able to fit perfectly around the nucleus You can’t fit the electrons wavelength if the orbit is smaller or bigger than some multiple of this wavelength. In order of the electron “wave” to fit the energy level the circumference of that energy level must be equal to a whole number of wavelengths not ↳ stable so electron electron cannot be in Stable- in this abit energy - wel - [PHYSICS 30] 14 zizumfewn elhorns a energy level n= · ] Recall that the wavelength of a par cle can be expressed as These are essen ally the same condi ons that Bohr found and as a result the wave nature of mater provides a natural explana on for quan zed energy levels # Explaining Orbits Beyond Hydrogen Consider Helium, the extra proton exerts a greater force on the electrons and draws them into a smaller orbital radius - The electron’s velocity adjusts, so now it has a different wavelength. This means the radius has - to also be different. - He Electron as a wave Instead of the electron being a particle “orbiting” the nucleus its mass and charge can be thought of as being spread out like a standing wave o The electron is not really at any one position like a particle would be, but everywhere a wave would be – Quantum Indeterminacy Even as a wave, the electron exists mostly right near the Bohr orbit Also explains the fine structure of emission spectra since sometimes the electron is a little higher or lower than the Bohr orbit when it makes a transition Can also explain why some lines are brighter than others The Quantum Model of the Atom is the Longest Lasting Model - ~ T O [PHYSICS 30] 15  The Nucleus Chemistry is concerned about electrons as they are responsible for determining how atoms bond Nuclear physics is concerned with the nucleus since this determines what the element is as well as the type of nuclear reac ons it can undergo Meet the Nucleons nucleus A nucleon is any particle that is contained in the ___________________ Protons + o _________ p o Positive charge +e o Number of protons (Z) = atomic number o Protons determine the element Neutrons no o ________ o No charge o Number of neutrons (N) = total nucleons (A) – atomic number (Z) Nuclear Nota on (total nucleons mass symbol from 5 the no + p+ A/1-atomic periodic table ↳ number p- atomic number of = from Isotopes periodic table Same element but different number of neutrons Even one additional neutron can significantly affect the stability of the nucleus. In an unstable nucleus the number of neutrons party determines the rate at which the nucleus decays and releases radiation [PHYSICS 30] 16  1. A nucleus has 7 protons and 8 neutrons. Identify what element it is, and write its symbol using ↑ pt- proper nuclear notation nitrogen # A = 7 + 8 = 15 2. If a nucleus has the symbol 23 11𝑁𝑁𝑁𝑁 provide as much informa on as you can about it. Atomic = Mass Units Bodium neutrons : 23-11 = 12 PT = 11 nucleous = 23 Atomic Mass Units Not an SI unit but it is useful because the numbers are more manageable. 1u 27kg - Based on carbon-12 = 1 66 x10. Subatomic Particle Mass (kg) Mass (u) 27 Neutron 674920x10 = 1. 1. 008665 27 Proton 1. 672 614 1 - x 10. 007276 Electron. 10956 9 x 10 - 31 0. 000549 The Strong Nuclear Force Why don’t nuclei fly apart due to the electrostatic force of repulsion between protons? Well, turns out there is another force, called the strong nuclear force that holds the nucleus together o It acts over a very short distance (the protons have to pretty much be touching each other) As we add more nucleons the batle between the strong nuclear force and the electrosta c force becomes stronger. + ↓ [ & n Binding Energy of the individual mass The sum of theAneutrons, protons and electrons in an atom is always slightly more than the actual atomic mass. This is because some of the mass of the atom exists as energy. [PHYSICS 30] 17  binding This is called the ____________________________ and it is the amount of energy that was converted from mass in order to bind the particles together. The binding energy is also the energy needed to separate all of the nucleons in an atom’s nucleus. mass defect The _________________________ and the actual atomic mass. is the difference between the calculated mass of an atom Am = Mcalculated Mactual - OR Am Mnucleons Mnucleus - = greater The mass of the individual subatomic par cles is _____________________ than the mass of the Hydrogen-2 atom. The mass defect is 0.002 388 u. That missing mass provides the energy to hold the neutron and proton together. Remember This missing mass isn’t actually missing, it has been converted into energy according ot Einstein’s mass equivalence equation. If we are using atomic mass units we must convert the answer into kilograms before substituting the mass into E = mc2 3. Determine the mass defect (in kilograms) and binding energy (in MeV) of Neon-20, with an actual mass of 19.992 440 u. [PHYSICS 30] 18  Mnucleus = 19 99244 Ou. Ne 10 p+ 20-10 = 10 no Am = ? E ? 1 of individual =. Determine mass nucleons C = 3 00. x 108 mis Mnucleons = 10mp + 10mn 1 00727bu Mp =. Mn = 1 008665. u = 10(1 00727bu). + 10/1 008665u). => 20 1594/u. 2. Calculate Am *m Mnucleons Nucleus = - 20 15941n. = 19 992440. u 0 16697/(66x10-254g) =. In 3. = 2. 7884x10-28kg79x109) Calculate binding energy E = smc2 = (2 7884x10-. 28kg)(3. 00 x 10/s)2 2 50956 10-" (40-1x) =. x = 156 8 x 10 eV Mex. = 156 8 Mev. =  the given. ie. mass of When do we ignore the electron? - L atom instead of When calculating the mass of the nucleus – don’t ignore the electrons nucleus Calculate the binding energy when you’re given the mass of the nucleus – ignore the electrons Binding Energy per Nucleon This graph gives the binding energy per nucleon. In order to find the total binding energy, you must mul ply this number by the number of nucleons. 4. Find the binding energy of Oxygen-16 nucleus. Total E =n)(cons) => 8 Mey (16) = 128 MeV subtract e of mass -to find Mnucleus 5. The mass of a zirconium-93 atom is 92.90647 u. Determine the mass of the nucleus, the mass defect, and the binding energy of this isotope. [PHYSICS 30] 19  9 zu 1. Calculate Mnucleus HOP Mnuc = Math 40 me 93 - 40 53n0 = * Matm = 92 90647u. = 92 90647u. - 40(5 485799x10 u). 88452684 66x02 kg) = 92. mp = 1 00727 bu 485799x10. my = 1. 0086btu nu = 1. 54x10-25 my me = 5. C = 3 00. x108 m/s I. Calculate mass defect Am = Mnucleons Mnuc = [40mp 53mn) + - 92 88452b8u. => (40(1 00727bu). + 53(1. 008665u)] - 92 88452b8u. 0 8657582u) 1 43716x =. =. #m 44 10-27 kg = 1. x. Calculate 3 kinding energy E = Amc 27kg)(3 x0m/s) 2 = (1 43716x10-.. 00 = 1 2934x10-105. = 8 08N0V. #08MeV  Radioactive Decay What is Radioac ve Decay? Radioac ve decay is the process by which the nucleus of an unstable atom spontaneously disintegrates, releasing __________________ energy and matter _______________________. The first documented observa on of radioac ve decay was 1896 when Henri Becquerel no ced that a uranium sample le an image on photographic film. This discovery led to much excitement and research into the decay of the nucleus of the atom which has brought us many technologies as ___________________, X-rays medical nuclear power treatments and the ability to harness __________________.. Alpha Decay, α – decay Alpha decay is one of the most common forms of radioac ve decay. Alpha decay involves the emission of helium a ________________________ nucleus (2 protons and 2 neutrons) from the decaying atom. To determine the daughter atom of the alpha decay reac on simply subtract 2 from the parent atom’s atomic number. This is the atomic number of the new atom. To determine the daughter atom’s atomic mass subtract 4 from the parent atom’s mass. The general equa on for alpha decay is as follows: - Where ye X represents the parent atom Y represents the daughter atom A represents the atomic mass and Z represents the atomic number [PHYSICS 30] 20  1. Show the decay equation for the alpha decay of 248 = 4+A A 248 4 - 240m - He = a. Curium – 248 = 244 b. Radium – 223 Du 96 z = = 2 + 96 2 2 - 23 Ray 223 A = = 219 A+4 = 94 R 88 2 = = 2 2 86 + Beta Decay, β – decay There are 3 main types of beta decay. These all involve the emission of a beta particle, which is either an electron __________________ or a _______________________. position Beta-nega ve Decay positive electron nuclureIf an atomic from the In the beta-nega ve decay the parent atoms emits an electron ______________________. nucleus contains too many neutrons the _________________________ repulsion becomes much stronger than face the strong nuclear force. In order to maintain the stability of the atom a neutron will spontaneously decay into a proton and an electron. The proton remains in the nucleus, increasing the atomic number, but not the mass. The electron (the beta par cle) is ejected from the nucleus. (An electron an neutrino is also ejected). The general equa on for beta nega ve decay is as follows: X + - Y + ie + r antineutrino , O must be - is included T !n jp +Ye + > - 2. Show the decay equation for the beta negative decay of 35 - A + 0 a. Sulphur – 35 355 - y + je 16 * + 5 A = 3S 16 = 2 - 1 b. Thorium – 234 Per 2 = 17 A 234 23Thy = 90 = 2 - 1 z = 9/ ⑳Pa [PHYSICS 30] 21 Beta-Posi ve Decay Similar to beta-nega ve decay, in a beta-posi ve decay a nucleon undergoes transmuta on and an proton ejec on occurs. A ___________________ changes into a __________________ neutron and a __________________ position (the an -par cle of an electron). The ________________________ position is ejected from the nucleus. The neutron remains in the nucleus so the atomic mass remains the same, but the atomic number decreases by one. The general equa on for beta-posi ve decay is as follows: - &x - zy + ye + r ↑ neutrino must OR 3 be included ip > - In + ye + v 3. Show the decay equation for the betta positive decay of a. Sodium – 22 + Ex 22Na + r = Pe b. Calcium – 39 Pine 39caB Electron Capture B no particle is ejected from the Electron capture is a different type of beta decay in which _____________________ electron nucleus. Instead, the nucleus captures an _______________________ which combines with a proton to form a neutron. The atomic mass remains the same and the atomic number is reduced by one. The general equa on for electron capture is as follows: iP + >H i - Ex + c + Y [PHYSICS 30] 22  4. Show the decay equation for the electron capture of a. Potassium – 40 4 Ar b. Carbon – 11 B Gamma Decay, ϒ decay high-energy A er an atom undergoes alpha or beta decay the daughter nucleus is in a _______________________ a photon state. The excited nucleus will spontaneously emit a gamma ray (________________________) to move into the lower, more stable energy state. The photon has neither ____________________ mass nor charge _________________, so the parent atom and the daughter atom are the same, just in different energy states. We will use an asterisk (*) to indicated an excited energy state. The general equa on for gamma decay is as follows: * X - EX + gz 5. Show the decay equation for the gamma decay of a. Curium – 244 2Cm 82 244 * (m > - + 96 [PHYSICS 30] 23  Dangers of Radioac ve Decay Alpha par cles, beta par cles and gamma rays all pose a risk to humans. They are all considered to be ionizing radiationmeaning they all have the poten al to remove _____________________ _________________________ electrons from atoms. In terms of energy of the emited par cles the types of radia on from lowest to highest are: Alpha Beta Gamma The major result of being exposed to ionizing radia on is the damage of the cell's DNA _____________________. The damaged DNA may cause the cell to die or may cause the cell to grow and divide out of control. When cell division is tumor uncontrolled this is called a ______________. If the tumor spreads to cells of Cancer other parts of the body this is called ______________________. Decay Series Sometimes the daughter nucleus itself is unstable and it will also decay By this process a nucleus may undergo several decays before reaching a stable arrangement This bunch of decays is called a decay series. 6. Determine how much energy is released when Uranium-238 decays to Thorium -234 mu = 238 050788u. 230Th + He 234 043 bolu Min Mu-[mintMie] = Am. = Whe = 4 0026034. = 238 050788u. - [234. 0026034] 04360n + 4. c = 3 00 x. 108 m/s = 0 004584. = 7. 60944x10- 30kg E = smc = (7 60944x10-. 30kg)(3. 00 x 108m/s)2 = 6 85. x 10-135 = [PHYSICS 30] 24  Decay Rates Activity = - A The way in which one unstable nucleus will decay is difficult to predict, but many nuclei tend to follow a predictable patern. Half-Life The rate of decay of radioactive substances is measured by a scale of time called the half-life A half-life is the time required for one-half of the atoms in any sample of a radioactive isotope to decay total time n 11 = N = Non ↑ F length of hale total N amount remaining = number No= amount started of half-lives with elapsed 1. Carbon-14 has a half life of 5730 years. How long will it take for the quantity of carbon-14 in a sample to drop to one-eight of the initial quantity? shafen ty = 5730y t = 3 t nt /2 = = = 3(5730y) +2= 19x10"ge( 2. Radon-222 has a half life of 3.82 days. What percent of the sample of this isotope will remain after 2 weeks? ty = 3. 82d n = ( 3 6649 % # (+ x 100 =. t = 2 weeks = = 0. 07884x100 3 6649 % = = 14d. % 8 [PHYSICS 30] 25  3. Marie Curie had a 76 g sample of polonium-210 (half-life = 138 d) in a box. After 3.8 years of refining radium, she goes to the box to get her polonium. Determine how much polonium-210 is in the box 0. 072g 4. You have 70 g of lead-212. It has a half-life of 10.6 h, determine how long it will take until only 3 =y 9.3 g remains. 3 No = 70g 70g = 2 = 35g n = t ht yz 9 3g 35g = 2 17 5 = N = = ge.. = 3(10 6h) ty 10 6h 17 5g + 2= 8 75g. = h... t = ? 5. Determine the half-life of iodine-121 using the graph 10 9d-2. 6d = 8 3d.. 8 0d.2d -1 2d 9 =.. 13 56-6 2d = 73... 242 6 d 6 20 210 9 d 1.. 13 5 9.... [PHYSICS 30] 26  Fusion & Fission Fusion Nuclear fusion reactions involve the fusing of two smaller nuclei to form a larger nucleus. Fusion reactions can occur multiple times to produce larger and larger nuclei. Nuclear fusion reactions are the source of many elements Fusion reactions occur naturally in stars The incredibly powerful force of gravity within the star allows the atoms to be close enough for the strong nuclear force to take effect. A star may start with lots of hydrogen gas that will fuse to form helium, then lithium and many other elements up to iron Nuclear fusion releases incredible amounts of energy It takes more binding energy to hold the nucleons of two separate small atoms together than it does of a larger atom When the small atoms fuse together, that excess binding energy is released In stars, the temperature, pressure and density of the nuclei allow for countless fusion reactions to take place, releasing a lot of energy. The most basic of these reactions is the proton-proton chain Man-made nuclear fusion has been achieved, but it is not yet able to generate electricity in a sustainable way. Technologies are being developed to magnetically confine the reactants in order to achieve nuclear fusion When successful, these technologies will provide the world with a clean energy source with no harmful waste products Will this end the world’s energy crisis? o Video [PHYSICS 30] 27  proton-proton chain 1. 2 it H + &B + p (twice) 2. IH + &H > - He + 5 (twice) 3. 23 He-He + 2,H + y 4 iB + B > - 25 (twice Total : 4H-He + 2iB + 20 + 78 (26 71MeV). Fission Nuclear fission reactions involve the breaking down of a larger atom into multiple smaller atoms. Nuclear fission can occur multiple times to make smaller and smaller atoms Nuclear fission releases lots of energy because it takes more energy to hold the large parent atom together than it does the smaller daughter atoms Nuclear fission has been used in nuclear weapons but also in nuclear energy production Even with the causalities of bombing and meltdowns, nuclear fission has caused less deaths than other energy generation methods like coal and fossil fuels. Nuclear energy from fission reactions is a very clean and safe form of energy if done properly. o Fission video Two common Uranium reac ons 23 + - + a + 3 23 + in No ce that both reac ons produce mul ple neutrons. These can be used to ini ate further fission reac ons. Both reac ons are exothermic. Reactors use control rods or a moderator to control the rate of reac on Made of elements such as boron and cadmium which are very good at absorbing neutrons If we want to allow more reactions to occur we remove the control rods If we want to slow down the reactions we insert the control rods further into the reactor. CANDU reactors use heavy water (water that contains hydrogen with an extra neutron) as the moderator o Chernobyl used graphite control rods that ignite when exposed to air. [PHYSICS 30] 28 Cri cal Nuclear Reac on => Occurs if only one of the neutrons in each reaction goes on to trigger an additional reaction. This is sustainable and controllable. 8 - - Supercri cal Nuclear Reac on n etc If two or more neutrons give rise to more reactions the increasing rate of reaction is called supercritical. Each reaction leads to multiple reactions and the number of reactions occurs exponentially. - - 1 -n So - n In etc u -so-o-- - -n -n - -n When do we want this to happen: o A nuclear bomb o When a nuclear power plant is just being started up (eventually its stepped down to just critical) When do we not want this to happen? o When the reactor is at risk of going into meltdown Subcri cal Reac on Not every reaction triggers a second reaction and eventually the reaction will die out We would want this to happen when we are shutting down a reactor 1. Calculate the energy released by the fission of Uranium that produces Barium – 141, Krypton – 92, and three neutrons [PHYSICS 30] 29  235 141 92l + on > - sBa + kr + 30n 235 04393u. 100866Su 140 9144124 91 9261564.. 1 008665u. C = 3. 00 x 108 m/S Am = Mr - mp = (235. 043930u + 1. 008665u] - [ 40. 914412u + 91 92615u. + 311 008665u)]. g) 186032u Long - 0. = 3 088x10-. E = Amck = (3. 088x10-28kg)(3 00x100m/s) 2. = 2. 7793x10" J = 1 74. x0 Mer Detecting and Measuring Subatomic Particles 17.1 & 17.3 Short History Recap Dalton - proposed the billiard ball model Thompson - discovered the electron (plum pudding model) Rutherford - discovered the nucleus and the proton James Chadwick - discovered the neutron in 1932 Carl Anderson - discovered the positron in 1932 Fred Reines and George Cowan - discovered particles called neutrinos in 1956 Murray Gell-Mann and George Zweig - independently proposed the existence quark in 1964 (the first of which was observed in 1968 and the last to be observed was in in 1995) Explosion of discovery of new particles 2012 - Observation of the Higgs Boson! But How do we OBserve these? If we’re dealing with macro-scale objects and you wanted to know how they interact, you would probably begin by suspending them at various separation distances and measuring the force between them ○ that’s how Coulomb determined the law of electrostatic repulsion and Cavendish measured the gravitational attraction between two objects But you can’t pick up a proton with tweezers or tie an electron onto the end of a string. For practical reasons, therefore, we have to resort to a less direct means to probe the interactions of elementary particles.  As it turns out, almost all our experimental information comes three sources: 1. Scattering events, in which we fire one particle and at another and record things like the angel of deflection 2. Decays, in which a particle spontaneously disintegrates and we examine the debris 3. Bound states, in which two or more particles stick together and we study the properties of the resulting object Developing a “Model” aka making and educated guess Ordinarily the procedure is to guess a form for the interaction and compare the resulting theoretical calculations with the experimental data. Of course the formulation of such a guess is guided by certain principles ○ Specifically special relativity and quantum mechanics Four Realms of Mechanics Small Classical Mechanics Quantum Mechanics large , slow small , slow Fast Relativistic Mechanics Quantum Field Theory large , fast small , fact HOw do we “See” Subatomic Particles Similar to how a hunter can use animal tracks to locate its quarry, physicists use particle tracks to identify and study particles. Two of the first devices that were used for particle detection are the Cloud Chamber and the Bubble Chamber Cloud Chamber Consists of air that is super saturated with vapour from a liquid like water or ethanol. The amount of liquid the air can hold depends on temperature and pressure. When air contains more vapour that it would normally hold at a given temperature and pressure it becomes supersaturated. As a result of this the liquid/vapour in a cloud chamber are not in equilibrium and any tiny disturbance (like that of a charged particle) can trigger the condensation of the vapour into droplets of liquid. Cloud Chambers A charged particle travelling through a cloud chamber will ionize some molecules along its path. The ions then trigger condensation, forming a miniature cloud along the path of the particle. This is similar to how the vapour trail formed by condensing exhaust gases shows the path of a jetliner through the sky. Cloud chambers were the main method of particle detection from the early 1900s to about 1960. Cloud Chamber Video Bubble Chambers Contains a liquified gas, like hydrogen, helium, propane or xenon. The pressure in the chamber is lowered so that the boiling point of the liquid is also lowered. The pressure in the chamber is reduced so that the boiling point is just below the actual temperature of the liquid As a result, when ions form from a charged particle moving through the liquid, these ions will cause the liquid to boil. This creates a trail of tiny bubbles along the path of the particle Bubble chambers are actually the reverse of the process used in cloud chambers (ie turning a liquid into a vapour as opposed to a vapour turning into a liquid)  -particle with zeo change Neutral Particles > - gamma ray Or EMR Do not create tracks in either a cloud or bubble chamber We can still observe them based on how the tracks of charged particles interact with the neutral particles we can’t see ○ For example, two identical, oppositely charged particles appear to be created from nothing would indicate they were probably created by a neutral particle or gamma ray  CERN Image 2650, Analyzing Particle Tracks 24 GeV protons, tracks highlighted And By applying a magnetic field across the chamber we can cause charged Image 2722, 24 GeV protons, particles to follow a curved or tracks spiral path highlighted Measurements of these tracks can be O used to determine the mass and charge of the particles. Often a photograph of a chamber will =>recedent show numerous tracks from many : Same different particles. Once in a while, sign a single track will suddenly appear o range to branch into several diverging tracks suggesting that the original particle has transformed into two or ↑ t opposite direction :: opposite & more different particles sign of charge ↑ ↑ Photographs of the tracks can be analyzed knowing that Positive and negative particles curve in opposite directions ○ Negative particles obey the 3rd LHR ○ Positive particles obey the 3rd RHR Lighter particles tend to curve more than heavier All conservation laws (eg, momentum charge) must be obeyed Neutral particles don’t leave tracks You and your lab partner are responsible for identifying the tracks of subatomic particles through a bubble chamber. Above is the picture you are working with and your partner has already identified track A as being produced by a Compton electron. B e => Compton produce Assume that tracks C and - D were made by particles moving at a speed of 0.10c through a into Scattering uniform magnetic field of 30 mT [out of page the page] and that the initial radius of each track is 5.7 mm. Determine the charge-to-mass ratio of the particles. Then, make a hypothesis about what the particles are. + positive large Fr = Fr Recall - ~ g ① = RHR x10" Eng 1 76 CIRg =. ↑ Frot WAR = · B is an e- electron and C V B = = 0 30. 101 x = 10 3 -. 37 0x107m/s xm = 0x10 - 3 is + ) a position 7x18-3u 1 75 10" Cleg = v = 5.. x 1 8X10"C/lg =. Energy Requirements 13.6 eV - ionize a hydrogen atom Few hundred eV - study the electron shells of atoms and molecules 10 MeV- overcome electrostatic repulsion and measure the nucleus Within the nucleus the strong nuclear force is a hundred times stronger than the electromagnetic force. This means that probing the structure of stable particles like protons and neutrons requires even more energy. Particle Accelerators provide us with the ability to do this Particle Accelerators - Van de Graaff Van de Graaff: A moving belt transfers charge to a hollow, conductive sphere, building up a large potential difference. This potential difference then propels ions through an accelerator chamber Particle Accelerators - Drift Tube Drift Tube: An alternating voltage accelerates charged particles through a series of electrodes shaped like open tubes. The applied voltage reverses as the particles pass through each tube, so the particles are always attracted to the next tube in the line Drift tubes in a prototype for Linac4 at CERN Particle Accelerators - Cyclotron A magnetic field perpendicular to the paths of the charged particles makes them follow circular paths within two hollow semicircular electrodes. An alternating voltage accelerates the charged particles each time they cross the gap between two electrodes. THe radius of each particle’s path increases with its Medical Isotope speed, so the accelerated particles Cyclotron spiral toward the outer wall of the cyclotron Particle Accelerators - Synchrotron This advanced type of cyclotron increases the strength of the magnetic field as the particle’s energy increases, so that the particles travel in a circle rather than spiralling outward. Some of the largest and most powerful particle accelerators are synchrotron rings Units for Subatomic Masses Particle physicists find it convenient to use units that are written in terms of energy/speed of light squared. 7827x10-36kg Find in ev Mea ↓ ev 1 or energy =. and write units as MeVI for x10-30 mass Mev 1 7827 1 =. E = mc2 x108m/s) 2 - kg)(3 3 masse > (11x10 - =. 00 = 8 199x10. - 45 = 5. 12438eV Tomato = 0 512 x 106 ev 0 512 Mev Side. =.. Practice Pg. 834 #1,2 Pg. 835 #1-7 Pg. 844 #1-4  Detecting and Measuring Subatomic Particles Quick History ReCap Dalton - proposed the billiard ball model Thompson - discovered the electron (plum pudding model) Rutherford - discovered the nucleus and the proton James Chadwick - discovered the neutron in 1932 Carl Anderson - discovered the positron in 1932 Fred Reines and George Cowan - discovered particles called neutrinos in 1956 Murray Gell-Mann and George Zweig - independently proposed the existence quark in 1964 (the first of which was observed in 1968 and the last to be observed was in in 1995) Explosion of discovery of new particles 2012 - Observation of the Higgs Boson! But How do We Observe These? If we’re dealing with macro-scale objects and you wanted to know how they interact, you would probably begin by suspending them at various separation distances and measuring the force between them o that’s how Coulomb determined the law of electrostatic repulsion and Cavendish measured the gravitational attraction between two objects But you can’t pick up a proton with tweezers or tie an electron onto the end of a string. For practical reasons, therefore, we have to resort to a less direct means to probe the interactions of elementary particles. As it turns out, almost all our experimental information comes three sources: 1. Scattering events, in which we fire one particle and at another and record things like the angel of deflection 2. Decays, in which a particle spontaneously disintegrates and we examine the debris 3. Bound states, in which two or more particles stick together and we study the properties of the resulting object Developing a “Model” AKA Making an Educated Guess Ordinarily the procedure is to guess a form for the interaction and compare the resulting theoretical calculations with the experimental data. Of course the formulation of such a guess is guided by certain