Physics 30 June 2000 Diploma Exam

# 22 written response question 2 begins on the next

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Unformatted text preview: in Supernova SN1987A Time Luminosity (Days) (1035 W) 0 1.000 50 0.638 100 0.407 150 0.260 200 0.166 250 0.106 300 0.067 350 0.043 The most likely reason that the luminosity decreased is that luminosity depends on the radioactive decay of isotopes created in the explosion. One source of the luminosity could be the gamma rays that result from any one of the decay chains listed in the following table. Radioactive Decay Chains (Showing Half-Life and Gamma Ray Energy) 56 6 Ni .1 day → 0.158 MeV 57 272 day Co → 77.3 Co day → 56 57 0.122 MeV 22 2 605 year Na . → 67 year Ti → 0.0783 MeV 60 22 Ne 2 44 Sc .day → 44 0.2712 MeV 6 1 Fe .5 × → 10 year 5 7 Al .1 × → 10 year 44 Ca 5 Co .27 year → 60 0.0586 MeV 26 Fe Fe 1.275 MeV 44 56 1.238 MeV 1.173 MeV 26 1.809 MeV 60 Ni Mg NOTE: The time provided above the arrow in each decay is the half-life. The energy provided below the arrow in each decay is the gamma ray energy. 24 Written Response — 15% 2. • Plot a graph of luminosity versus time. • Determine the half-life of the luminosity, and identify the single decay believed to be responsible for most of the energy released by the supernova. • The amount of radioactive nickel-56 predicted to have been created in the supernova is about 1.49 × 1029 kg. How many days would it take for the mass of nickel-56 to be reduced to 1.86 × 1028 kg? • The decay chain 60 Fe → 60Co → 60 Ni shows two radioactive decays. Write the nuclear decay equation for iron-60. Provide the name of the particle emitted. • Identify the decay chain in the table that releases gamma rays with the shortest wavelength. Explain why you identified this decay chain, and calculate the shortest gamma wavelength. Clearly communicate your understanding of the physics principles that you are using to solve this question. You may communicate this understanding mathematically, graphically, and/or with written statements. (Title) 25 You have now completed the examination. If you have time, you may wish to check your answers....
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