PHYSICS SAC 2009 NUCLEAR AND RADIOACTIVE PHYSICS Name__________________________________________________________ Circle the best response: 1. Which of the following can be the isotope of A 14 14 N B 16 7N 14 7N C 14 8N D 14 6N 2. An alpha particle consists of A 2 protons and 2 electrons B 4 protons C 2 protons and 2 neutrons D 2 neutrons and 2 electrons 3. The radiation which is deflected most by a magnetic field is? A gamma rays B neutrons C alpha particles D beta particles 4. A radioactive source emits one type of radiation only. On investigation it is found that the rays will penetrate quite well through 1mm of aluminium, but will not penetrate 1cm of lead. The radiation emitted will most probably be A beta particles B alpha particles C infrared rays D 5. Which of the following statements about radioactive elements is correct? A B C D Radioactive elements produce no radiation at low temperatures. Radioactive elements produce only electromagnetic waves. All radioactive elements produce X-rays. In radioactive elements, the nucleus explodes spontaneously. 6. Strontium-90 decays by radioactive emission to form yttrium-90. 90 The equation is 90 38 Sr 39 Y + X + , the atomic and mass numbers for X are A 1, 1 7. When an atom undergoes -decay A The mass number increases by 1 and the atomic number is constant B The mass number decreases by 4 and the atomic number decreases by 2 C The mass number decreases by 2 and the atomic number decreases by 4 D The mass number is constant and the atomic number increases by 1 B 0, 0 C -1, 0 D 0, -1 gamma rays 8. -rays are A electromagnetic radiation C positively charged particles 9. B D negatively charged particles uncharged particles The radioisotope 25Na has a half life of 1 minute. Approximately what percentage of a sample remains after 3 minutes A 50% B 33% C 25% D 12.5% Question 10 &11 relate to the following. A Geiger counter is used to measure the radioactive disintegrations from a sample of a certain radioisotope. The count rate recorded is shown in the graph below 5 Activity (×1012 Bq) 4 3 2 1 0 10. 5 10 20 25 30 time (H) What is the half-life of this sample? A 5 hours 11. 15 B 10 hours C 15 hours D 20 hours What is the activity (× 1012 Bq) after 3 half lives A 3.5 B 2.5 C 1.7 D 0.6 12. When a 228 90 Th nucleus undergoes radioactive decay by the emission of an alpha particle the new nucleus formed is A 228 89 Ac B 228 90 Ac C 224 88 Ra D 224 87 Fr 13. When tellurium-130 ( 130 52 Te) is bombarded with neutrons (inside the core of a nuclear reactor) it forms a very unstable tellurium-131 and a gamma ray. The equation for this process is A 130 52 Te C 130 52 Te 14. An electronvolt equals 1.6 10-19J. How much energy in Joules does a 4.2MeV alpha particle have? A 1.6 10-19J B 6.72 10-13J C 6.72 10-19J D 3.81 10-26J 131 52 Te + 01 n + 01 n + 131 52 Te + B 130 52 Te D 130 52 Te + 2 01 n 131 52 Te + 2 01 n + 131 52 Te + Short Answer 1. The Helium ion a. Protons 3 2 He2+ has what number of each of the following? b. Neutrons c. Electrons 2. An atom of an element contains 20 electrons and 20 neutrons. a. What is its nuclear symbol? b. What is its mass number? c. What is its atomic number? 3. Thorium_234 emits a beta particle and a gamma ray as it decays. Write a nuclear equation for this decay. 4. The decay series starting with Uranium-238 and finishing with Lead-82 is a naturally occurring series as follows. 238 92 U 21 0 83 Bi 234 90 Th 21 0 84 Po 234 91 Pa 234 92 U 230 90 Th 226 88 Ra 222 86 Rn 21 8 84 Po 21 4 82 Pb 206 82 Pb a. Which nuclide is stable in this series? b. Which nuclide is the daughter of Thorium-230? c. What type of radioactive decay does Radium-226 undergo? d. Write the nuclear equation for the decay of lead-214 to Bismuth-214 21 4 83 Bi 21 4 84 Po 21 0 82 Pb 5. The half-life of Radium-226 is 1600 years. Draw a graph of the decay of a 2.0 gram sample over time. a What fraction of the element remains after 6400 years? b How long does it take for 1.5 grams of the radium to decay? c How much radium will remain after 4000 years? 6. Why is α-particle radiation from a radioactive source likely to be less harmful to living organisms than β-radiation or γ-radiation? PART 3 Choose 2 questions to answer from the possible 6 below 1. a). The nuclear bomb dropped on Hiroshima during world war two used Uranium-235. Describe how the bomb worked, include the following in your answer – fission, critical mass, chain reaction. b). Describe three ways in which a nuclear bomb causes death. 2. a). A nuclear reactor uses a controlled chain reaction to produce power. What is meant by “controlled” and how can this control be achieved? b). Nuclear power is a debatable issue across the world. Give a reason for both sides of the debate (one for and one against nuclear power). 3. a). State two reasons why isotopes the emit alpha radiation are not used as medical tracers. b). 10 Sieverts of radiation will cause death in about ½ an hour. Explain why then are some tumors exposed to 25 Sieverts of radiation in medical procedures? 4. a). Describe two ways in which radioactive isotopes can be used in industry (include the benefit of using this technology. b). How are workers protected when working with radioactive nuclides? How is this monitored? 5. a). Natural radiation contributes to the sources of this natural radiation? about 88% of human exposure to radiation. What are b). The background radiation dose that we receive each year is about 2 – 3 mSv. Describe three factors that could affect this amount. 6. a). Carbon-14 is natural form of radiation occurring in nature. Describe how it is formed. b). The Jurassic era is known as a time on Earth when many dinosaurs roamed the world. This period of time occurred around 150 to 200 million years ago. Is carbon dating is a suitable and accurate method of determining the age of a dinosaur bone from this period? Explain (the half life of carbon-14 is 5670 years).