Nuclear Physics 2. D. atomic energy levels. (1) D. scattered back along the original direction. (1)

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Leo Goodwin
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1 Name: Date: Nuclear Physics 2. Which of the following gives the correct number of protons and number of neutrons in the nucleus of B? 5 Number of protons Number of neutrons A. 5 6 B. 5 C. 6 5 D The emission and absorption spectra of different elements provides evidence for the existence of A. isotopes. B. neutrons. C. protons. D. atomic energy levels. 3. In the Geiger-Marsden experiment, α particles are scattered by gold nuclei. The experimental results indicate that most α particles are A. scattered only at small angles. B. scattered only at large angles. C. absorbed in the target. D. scattered back along the original direction. 4. The nucleus of an atom contains protons. The protons are prevented from flying apart by A. the presence of orbiting electrons. B. the presence of gravitational forces. C. the presence of strong attractive nuclear forces. D. the absence of Coulomb repulsive forces at nuclear distances.

2 5. Which one of the following diagrams best illustrates the first two stages of an uncontrolled fission chain reaction? A. Key: neutron uranium nucleus fission fragment B. C. D. 6. The graph below shows the variation with mass (nucleon) number of the average binding energy per nucleon. 0 mass number average binding energy per nucleon II I IV III Which direction indicates a fission reaction with a release of energy? A. I B. II C. III D. IV 2

3 7. This question is about nuclear fission and nuclear fusion. (a) Compare the processes of nuclear fission and nuclear fusion (4) (b) A nuclear fusion reaction that is being investigated for the production of power is 2 H + 3 H 4 2 He + 0 n + ( J) where the energy liberated in each reaction is Determine the rate, in kg s, of production of J 4 2 He required for a power output of 00 MW (Total 6 marks) 8. This question is about the production of nuclear energy and its transfer to electrical energy. (a) When a neutron collides with a nucleus of uranium-235 ( U) the following reaction can occur U + 0 n Ba + 36 Kr n (i) State the name given to this type of nuclear reaction... Energy is liberated in this reaction. In what form does this energy appear?.. (b) Describe how the neutrons produced in this reaction may initiate a chain reaction

4 The purpose of a nuclear power station is to produce electrical energy from nuclear energy. The diagram below is a schematic representation of the principle components of a nuclear reactor pile used in a certain type of nuclear power station. control rods uranium ore fuel rods graphite block (moderator) The function of the moderator is to slow down neutrons produced in a reaction such as that described in part (a) above. (c) (i) Explain why it is necessary to slow down the neutrons (3) Explain the function of the control rods (d) Describe briefly how the energy produced by the nuclear reactions is extracted from the reactor pile and then transferred to electrical energy (4) (Total 2 marks) 4

5 9. This question is about nuclear energy. (a) Define nuclear binding energy (b) A neutron collides with a nucleus of uranium-235 and the following reaction takes place. 235 State the name of this type of reaction U + 0n 37Rb + 55Cs n... (c) The mass of nuclei can be expressed in terms of unified mass units (u). (i) Define the term unified mass unit. Using the data below, calculate the energy, in MeV, that is released in the reaction. massof mass of mass of mass of U = u Rb = u Cs = 37.92u 0 n =.0087 u (4) (d) Explain the importance of the two neutrons produced in the reaction.... 5

6 (e) Each neutron accounts for about 2 MeV of the energy released in the reaction. Suggest what accounts for the rest of the energy released (f) The reaction in (b) is more likely to take place if the colliding neutron has an energy of about 0. ev. In certain types of nuclear reactors in which this reaction might take place, the neutrons produced have their energy reduced by collisions with nuclei of graphite ( 2 C). The law of conservation of momentum can be used to estimate the number of collisions required to reduce the energy of the neutrons to 0. ev. State the law of conservation of momentum (g) A neutron has a kinetic energy of 2.00 MeV. Deduce that the speed of the neutron is m s (h) You may assume that the mass of a nucleus of graphite is twelve times the mass of a neutron. In a certain collision between a neutron and a stationary graphite nucleus, the neutron of kinetic energy 2.00 MeV, rebounds from the graphite nucleus in a direction along a line joining the centres of the nucleus and neutron. 6

7 m s m s v = m s neutron graphite before collision after collision The rebound speed of the neutron is m s. (i) Deduce that the speed v of the graphite nucleus after collision is m s. (3) Using your answer in (i), deduce whether the collision is elastic or inelastic. (3) (iii) Use your answer to to deduce that each time a neutron collides in this manner with a graphite nucleus it loses about 30% of its kinetic energy. (iv) State the fraction of the total initial energy lost by a neutron in its second collision with a graphite nucleus. (Total 25 marks) 7

Topic 7 &13 Review Atomic, Nuclear, and Quantum Physics

Topic 7 &13 Review Atomic, Nuclear, and Quantum Physics Name: Date:. Isotopes provide evidence for the existence of A. protons. B. electrons. C. nuclei. Topic 7 &3 Review Atomic, Nuclear, and Quantum Physics D. neutrons.. The atomic line spectra of elements