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Category > Physics Posted 05 Sep 2017 My Price 10.00

Alpha Decay - PhET Lab

Please provide assistance in answering the enclosed document that I require assistance in completing.

Lab 7Alpha Decay - PhET LabObjectivesTo better understand half-life, to draw a radioactive decay graph, and to determine thehalf-life time (t1/2) for Polonium - 211 (211Po)IntroductionUnstable atomic nuclei may decay into less energetic nuclei by emission of alpha, beta,and gamma radiation. These forms of radiation are now known to consist of4He nuclei (α-particle), electron, and high energy photons, respectively. The type of decay a nucleus mayundergo depends on how it is unstable. Many materials may emit more than one form ofradiation. This is especially true when the parent radioactive nuclei produce daughter nuclei thatare also radioactive. The parent nucleus is the original nucleus before decay and the daughternucleus is the resulting nucleus after decay.Nuclei with atomic numbers (number of protons, or Z) greater than 83 may all undergoalpha decay (however, the rate of decay may be so slow for some that it seems to be forever). Inalpha decay, a helium nucleus consisting of two protons and two neutrons is emitted from theparent nucleus. This reduces the atomic number of the original nuclei by two and its atomic mass(number of both protons and neutrons in the nucleus, or A) by four. We may express such anuclear decay by the nuclear reaction equation:±²³´µ±¶·²¶¸¹º»·¸(7.1)(parent)(daughter)(α-particle)For example,¼½¾¿·À·³ÁÂÃ÷·Ã¹º»·¸(7.2)In example 7.2, the total atomic number of Thorium decreases by 2 after alpha decayresulting in the daughter nucleus of Radium and the total mass number decreases by 4. In anuclear decay equation, the sums of the mass and atomic numbers will be the equal on each sideof the arrow. Figure 7.1 shows the decay series of Uranium - 238 (238U) to Lead - 206 (206Pb).The alpha particles are the most ionizing radiation emitted by natural sources (with theextremely rare exception of the spontaneous fission of uranium) and are stopped by as little as asheet of paper or a few centimeters of air (2-8cm) depending on their initial velocity. Alphaparticles that are emitted from a single type of source are monoenergetic, that is, they are allemitted with the same kinetic energy. Depending on the source, this energy ranges from 3-8MeVcorresponding to velocities of (1.4 – 2)×107m/s! Alpha particles play an important role innuclear physics.
 
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Half-lifeis the time it takes for half of the nuclei of a given sample to decay. In otherwords, after one half-life has expired only one-half of the original amount of radioactive nucleiremains undecayed. After 2 half-lives only one-quarter (½ of ½) of the original amount remainsun-decayed. We can use this property to perform radioactive dating.The expression that governs radioactive decay is,±²³´µ¶·(7.3)WhereNois the initial number of parent nuclei at t=0, andNis the number of parentnuclei any timet, and¸is the decay constant, or the probability per unit time that any onenucleus will decay. The half-life time then is,¹º»¼±½¾¿ÀÁ(7.4)Figure 7.1.Decay series of Uranium - 238 (238U) to Lead - 206 (206Pb).EquipmentA computer with minimum requirements: Microsoft Windows - XP or OS 10.5 andMacromedia Flash 9 or later and UPDATED JAVA. Be sure to have Java with Web Launcher.PhET Simulation “Alpha Decay”.
 
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Runhttp://phet.colorado.edu/en/simulation/alpha-decayFigure 7.2.Screen shot of ‘Alpha Decay’ from PhET Interactive Simulations.ProcedurePART 11.Choose “Multiple Atoms” option (Tab on top of page).2.Click to “Custom” from the column on the right of the screen.3.Adjust the half life to any value you choose that is between 0.5-1 second by clicking anddragging the double-sided green arrow. Estimate and record this value.4.Add all atoms to the screen from the bucket by clicking the ‘Add 10’ icon below thebucket at the bottom of the page.5.By clicking the play/pause button (center/bottom of page) start and stop the decayreaction every half second. Use the timer at the top of the page. Find how many parentnuclei (undecayed nuclei) remain at each time (upper left corner of page).6.Repeat your measurement 4 more times, record your data below and calculate averages.Half-life value you chose:_________secondsTime (s)00.51.01.52.02.53.0Number of parentnuclei (N)9999999999Average997.Draw number of parent nuclei vs. time on a graph. Compare your graph with the graph
 
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found on PAGE 625 of your textbook. Point out any similarities and differences.PART 28.On the right side on the screen, choose “Polonium - 211 to Lead - 207”.9.Add 20 nuclei of211Po (No) from the basket (i.e. click twice on ‘Add 10’).10.When the time t reaches 1 second, Record number of211Po (N at t=1.0 second). Do this 3times. Find the average value. Record this as N.11.By using formula 7.3, where t = 1, No= 20 and N is your average calculated from step10, calculate the decay constant.12.Using formula 7.4 andcalculated in step 11, calculate t1/2for211Po.Questions1.Tabulate your results.2.Plot number of parent nuclei remaining vs. time.3.Compare your graph with the graph found on PAGE 625 of your textbook. Point out anysimilarities and differences that you see.4.What is the shape of your graph? Did you expect that it should be a straight line?5.Should the graph pass through the origin? Explain.6.By using formula 7.3, calculate the decay constantfor211Po.7.Using formula 7.4, calculate the half-life (t1/2) for211Po.8.Write a brief error analysis for PART 2 of the experiment. What are your main sources oferror?What might you do differently next time to increase the accuracy of the measuredhalf-life of211Po?Thanks to:PhET Interactive SimulationsUniversity of Coloradohttp://phet.colorado.edu.
 
 

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AccountingQueen
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Status NEW Posted 05 Sep 2017 03:09 PM My Price 10.00

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