RI Chap 20 Nuclear Physics Lecture Notes

20 NUCLEAR PHYSICS H2 Physics 9478 Content Page 20.1 The Nuclear Atom 2 20.2 Radioactive Decay 10 20.3 Nuclear Processes and Conservation Laws 24 20.4 Mass Defect and Nuclear Binding Energy 26 20.5 Appendix 38 Learning Outcomes Candidates should be able to: (a) infer from the results of the Rutherford α -particle scattering experiment the existence and small size of the atomic nucleus. (b) distinguish between nucleon number (mass number) and proton number (atomic number). (c) show an understanding that an element can exist in various isotopic forms, each with a different number of neutrons in the nucleus, and use the notation XA Z for the representation of nuclides. (d) show an understanding of the spontaneous and random nature of nuclear decay. (e) infer the random nature of radioactive decay from the fluctuations in count rate. (f) show an understanding of the origin and significance of background radiation. (g) show an understanding of the nature and properties of α, β and γ radiations (knowledge of positron emission is not required). (h) define the terms activity and decay constant, and recall and solve problems using the equation AN λ= . (i) infer and sketch the exponential nature of radioactive decay and solve problems using the relationship ( )0 expxx t λ= − where x could represent activity, number of undecayed particles or received count rate. (j) define and use half-life as the time taken for a quantity x to reduce to half its initial value. (k) solve problems using the equation 1 2 ln2 tλ = . (l) discuss qualitatively the applications (e.g. medical and industrial uses) and hazards of radioactivity based on: (i) half-life of radioactive materials, (ii) penetrating abilities and ionising effects of radioactive emissions. (m) represent simple nuclear reactions by nuclear equations of the form 14 4 17 1 72 81N He O H+ →+ .

RAFFLES INSTITUTION YEAR 56 PHYSICS DEPARTMENT Page| 2 (n) state and apply to problem solving the concept that nucleon number, charge and mass-energy are all conserved in nuclear processes. (o) show an understanding of how the conservation laws for energy and momentum in 𝛽𝛽 decay were used to predict the existence of the (anti)neutrino [knowledge of the antineutrino and the zoo of particles is not required]. (p) show an understanding of the concept of mass defect. (q) recall and apply the equivalence between energy and mass as represented by 𝐸𝐸 =𝑚𝑚𝑚𝑚2 to solve problems. (r) show an understanding of the concept of nuclear binding energy and its relation to mass defect. (s) sketch the variation of binding energy per nucleon with nucleon number. (t) explain the relevance of binding energy per nucleon to nuclear fusion and to nuclear fission. 20.1 The Nuclear Atom  Introduction Just as the chemical energy liberated in fire can be used for good and evil, the energy in nuclear “fire” can also be put to benevolent or malevolent uses. A slow and controlled relea