© 2010 Pearson Education, Inc. PowerPoint ® Lectures for College Physics: A Strategic Approach, Second Edition Chapter 30 Nuclear Physics

© 2010 Pearson Education, Inc. Slide Nuclear Physics

© 2010 Pearson Education, Inc. Slide 30-3

© 2010 Pearson Education, Inc. Slide 30-4

© 2010 Pearson Education, Inc. Slide 30-5

© 2010 Pearson Education, Inc. Reading Quiz 1.The mass number A of a nucleus is the number of ___________ in the nucleus. A.protons B.protons plus neutrons C.neutrons Slide 30-6

© 2010 Pearson Education, Inc. Slide 30-7 Answer 1.The mass number A of a nucleus is the number of ___________ in the nucleus. A.protons B.protons plus neutrons C.neutrons

© 2010 Pearson Education, Inc. Reading Quiz 2.When a nucleus decays by giving off an electron, we call this ________ decay. A.alpha B.beta C.gamma Slide 30-8

© 2010 Pearson Education, Inc. Slide 30-9 Answer 2.When a nucleus decays by giving off an electron, we call this ________ decay. A.alpha B.beta C.gamma

© 2010 Pearson Education, Inc. Reading Quiz 3.________ decay results in a daughter nucleus that is the same as the parent nucleus. A.Alpha B.Beta C.Gamma Slide 30-10

© 2010 Pearson Education, Inc. Slide Answer 3.________ decay results in a daughter nucleus that is the same as the parent nucleus. A.Alpha B.Beta C.Gamma

© 2010 Pearson Education, Inc. Nuclear Structure Different isotopes of the same element have the same atomic number but different mass numbers. Slide 30-12

© 2010 Pearson Education, Inc. Checking Understanding How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4 Slide 30-13

© 2010 Pearson Education, Inc. Slide Answer How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4

© 2010 Pearson Education, Inc. Checking Understanding How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4 Slide 30-15

© 2010 Pearson Education, Inc. Slide Answer How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4

© 2010 Pearson Education, Inc. Checking Understanding How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4 Slide 30-17

© 2010 Pearson Education, Inc. Slide Answer How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4

© 2010 Pearson Education, Inc. Checking Understanding How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4 Slide 30-19

© 2010 Pearson Education, Inc. Slide Answer How many neutrons are in the following isotope? (The isotope may be uncommon or unstable.) A.8 B.7 C.6 D.5 E.4

© 2010 Pearson Education, Inc. Boron, with atomic number Z=5, has two stable isotopes, with atomic mass numbers A=10 and A=11. Boron’s chemical atomic mass is What are the approximate fractions of the two stable boron isotopes found in nature? A.92% 11 B, 8% 10 B B.80% 11 B, 20% 10 B C.50% 11 B, 50% 10 B D.20% 11 B, 80% 10 B E.8% 11 B, 92% 10 B Checking Understanding Slide 30-21

© 2010 Pearson Education, Inc. Slide Answer Boron, with atomic number Z=5, has two stable isotopes, with atomic mass numbers A=10 and A=11. Boron’s chemical atomic mass is What are the approximate fractions of the two stable boron isotopes found in nature? A.92% 11 B, 8% 10 B B.80% 11 B, 20% 10 B C.50% 11 B, 50% 10 B D.20% 11 B, 80% 10 B E.8% 11 B, 92% 10 B

© 2010 Pearson Education, Inc. Magnesium has three stable isotopes, with the following natural abundances: 79% of naturally occurring magnesium is 24 Mg, with u= % of naturally occurring magnesium is 25 Mg, with u= % of naturally occurring magnesium is 26 Mg, with u=25.98 What is the chemical atomic mass of magnesium? Slide Example Problem

© 2010 Pearson Education, Inc. Slide Stability

© 2010 Pearson Education, Inc. Binding Energy Slide 30-26

© 2010 Pearson Education, Inc. Binding Energy of a Helium Nucleus Slide 30-27

© 2010 Pearson Education, Inc. There are several elements for which there is only one stable isotope, or for which one stable isotope dominates the natural abundance. Three examples are: All but % of naturally occurring helium is the stable isotope 4 He. 100% of naturally occurring niobium is the stable isotope 93 Nb. 100% of naturally occurring bismuth is the stable isotope 209 Bi. What is the ratio of neutrons to protons for these three isotopes? 16 O, with u= , is stable; 19 O, with u= , is not. What is the binding energy per nucleon for each of these nuclei? Slide Example Problems

© 2010 Pearson Education, Inc. Curve of Binding Energy Light nuclei can become more stable through fusion. Heavy nuclei can become more stable through fission. All nuclei larger than a certain size spontaneously fission. Slide 30-28

© 2010 Pearson Education, Inc. Nuclear Forces Slide 30-29

© 2010 Pearson Education, Inc. Nuclear Energy Levels and Decay Different levels for neutrons and protons Energy difference between levels is very large Nuclei can become more stable through certain decay modes Slide 30-30

© 2010 Pearson Education, Inc. The beryllium isotope 11 Be decays to the boron isotope 11 B. a.Show the nucleons of both nuclei on the shell-model energy-level diagrams below. b.Explain why this decay is energetically favorable. Slide Example Problem

© 2010 Pearson Education, Inc. Nuclear Radiation Slide 30-32

© 2010 Pearson Education, Inc. Alpha Decay Slide 30-33

© 2010 Pearson Education, Inc. Beta Decay Slide 30-34

© 2010 Pearson Education, Inc. What is the daughter nucleus for this decay: 90 Sr → ? X+e- A. 90 Y B. 89 Y C. 90 Rb D. 89 Rb Slide Checking Understanding

© 2010 Pearson Education, Inc. Slide Answer What is the daughter nucleus for this decay: 90 Sr → ? X+e- A. 90 Y B. 89 Y C. 90 Rb D. 89 Rb

© 2010 Pearson Education, Inc. What is the daughter nucleus for this decay: 222 Rn → ? X+α A. 220 Po B. 218 Po C. 220 Ra D. 218 Ra Slide Checking Understanding

© 2010 Pearson Education, Inc. Slide Answer What is the daughter nucleus for this decay: 222 Rn → ? X+α A. 220 Po B. 218 Po C. 220 Ra D. 218 Ra

© 2010 Pearson Education, Inc. What is the daughter nucleus for this decay: 99 Tc → ? X+γ A. 99 Tc B. 99 Mo C. 99 Nb D. 99 Ru Slide Checking Understanding

© 2010 Pearson Education, Inc. Slide Answer What is the daughter nucleus for this decay: 99 Tc → ? X+γ A. 99 Tc B. 99 Mo C. 99 Nb D. 99 Ru

© 2010 Pearson Education, Inc. Slide Example Problem 11 Li is an unstable isotope of lithium. Sketch the energy level structure for the neutrons and the protons in this nucleus. What decay mode would you expect for this nucleus? Write the full equation for the decay you expect, including the daughter nucleus.

© 2010 Pearson Education, Inc. Slide Decay Series 235 U is unstable Through a series of alpha beta decay, settles on 207 Pb In a star, everything ends up as 56 Fe

© 2010 Pearson Education, Inc. Fission Slide 30-46

© 2010 Pearson Education, Inc. Slide Operation of a Geiger Counter

© 2010 Pearson Education, Inc. Example Problem: Activity Most of the internal radiation of the human body is due to a single isotope, the beta emitter 40 K, with half life of 1.28×10 9 years. The body contains about 0.35% potassium by mass; of this potassium, about 0.012% is 40 K. What is the total activity, in Bq, of a 70 kg human? Slide R = rN = ______ 0.693N t 1/2

© 2010 Pearson Education, Inc. Half Life Slide 30-44

© 2010 Pearson Education, Inc. Nuclear Decay Slide 30-45

© 2010 Pearson Education, Inc. Example Problems: Decay Times The Chernobyl nuclear reactor accident in the Soviet Union in 1986 released a large plume of radioactive isotopes into the atmosphere. Of particular health concern was the short-lived (half life: 8.0 days) isotope 131 I, which, when ingested, is concentrated in and damages the thyroid gland. This isotope was deposited on plants that were eaten by cows, which then gave milk with dangerous levels of 131 I. This milk couldn’t be used for drinking, but it could be used to make cheese, which can be stored until radiation levels have decreased. How long would a sample of cheese need to be stored until the number of radioactive atoms decreased to 3% of the initial value? Slide 30-46

© 2010 Pearson Education, Inc. Example Problems: Decay Times A scrap of parchment from the Dead Sea Scrolls was found to have a 14 C/ 12 C ratio that is 79.5% of the modern value. Determine the age of this parchment. Slide 30-46

© 2010 Pearson Education, Inc. Dose and Dose Equivalent 1 Gy = 1.00 J/kg of absorbed energy Dose equivalent in Sv = (dose in Gy) x RBE Slide 30-47

© 2010 Pearson Education, Inc. In a previous example, we computed the activity of the 40 K in a typical person. Each 40 K decay produces a 1.3 MeV beta particle. If 40% of the energy of these decays is absorbed by the body, what dose, and what dose equivalent, will a typical person receive in one year from the decay of these nuclei in the body? Example Problems: Determining Dose Slide 30-48

© 2010 Pearson Education, Inc. Summary Slide 30-50

© 2010 Pearson Education, Inc. Summary Slide 30-51

© 2010 Pearson Education, Inc. What is the decay mode of the following decay? 137 Cs → 137 Ba + ? A.Alpha decay B.Beta-minus decay C.Beta-plus decay D.Gamma decay Additional Questions Slide 30-52

© 2010 Pearson Education, Inc. Slide Answer What is the decay mode of the following decay? 137 Cs → 137 Ba + ? A.Alpha decay B.Beta-minus decay C.Beta-plus decay D.Gamma decay

© 2010 Pearson Education, Inc. What is the decay mode of the following decay? 222 Rn → 218 Po + ? A.Alpha decay B.Beta-minus decay C.Beta-plus decay D.Gamma decay Additional Questions Slide 30-54

© 2010 Pearson Education, Inc. Slide Answer What is the decay mode of the following decay? 222 Rn → 218 Po + ? A.Alpha decay B.Beta-minus decay C.Beta-plus decay D.Gamma decay

© 2010 Pearson Education, Inc. What is the decay mode of the following decay? 60 Ni* → 60 Ni + ? A.Alpha decay B.Beta-minus decay C.Beta-plus decay D.Gamma decay Additional Questions Slide 30-56

© 2010 Pearson Education, Inc. Slide Answer What is the decay mode of the following decay? 60 Ni* → 60 Ni + ? A.Alpha decay B.Beta-minus decay C.Beta-plus decay D.Gamma decay

© 2010 Pearson Education, Inc. Additional Example Problem A 60 kg laboratory worker receives a whole-body x-ray exposure of 0.50 mSv. The x-ray wavelength is 0.15 nm. How many x-ray photons are absorbed in the worker’s body? X rays have an RBE of 1. Slide 30-58