Chapter 32

Ionizing Radiation, Nuclear Energy, & Elementary Particles

AP Learning ObjectivesNuclear Physics Nuclear reactions (including conservation of mass

number and charge) Students should understand the significance of the

mass number and charge of nuclei, so they can: Interpret symbols for nuclei that indicate these

quantities. Use conservation of mass number and charge to

complete nuclear reactions. Determine the mass number and charge of a

nucleus after it has undergone specified decay processes.

Students should know the nature of the nuclear force, so they can compare its strength and range with those of the electromagnetic force.

Students should understand nuclear fission, so they can describe a typical neutron-induced fission and explain why a chain reaction is possible.

AP Learning ObjectivesNuclear Physics Mass-energy equivalence

Students should understand the relationship between mass and energy (mass-energy equivalence), so they can: Qualitatively relate the energy released in

nuclear processes to the change in mass. Apply the relationship E = (m)c2 in

analyzing nuclear processes.

Table Of Contents

1. Biological Effects of Ionizing Radiation (AP?)

2. Induced Nuclear Reactions

3. Nuclear Fission

4. Nuclear Reactors

5. Nuclear Fusion

6. Elementary Particles

7. Cosmology

Chapter 32: Ionizing Radiation, Nuclear Energy, & Elementary Particles

Section 1:Biological Effects of Ionizing Radiation (AP?)

Ionizing radiation consists of photons and/or moving particles that havesufficient energy to knock and electron out of an atom or molecule, thusforming an ion.

Exposure is a measure of the ionizing radiation produced in air by X-raysor γ-rays.

In passing through the air, the beam produces positive ions whose totalcharge is q. Exposure is the charge per unit mass of the air.

m

q

41058.2

1 roentgens)(in Exposure

Biological Effects of Radiation

For biological purposes, the absorbed dose is a more suitable quantitybecause it is the energy absorbed from the radiation per unit mass ofthe absorbing material:

material absorbing of Mass

absorbedEnergy dose Absorbed

kgJ1Gy 1

gray

gray 01.0 rad 1

Absorbed Dose

To compare the damage produced by different types of radiation, the relative biological effectiveness (RBE) is used.

effect biological same the

producesthat radiation of Dose

effect biologicalcertain a pruduces

that rays-X keV-200 of Dose

RBE

Differences in effect

The product of the absorbed dose and the RBE is the biologically equivalent dose:

RBEdose Absorbed

dose equivalently Biological

Effect on Organisms

32.1.1. Ionizing radiation can be harmful to living things because of which of the following reasons?

a) Cells may be destroyed by the thermal energy released by radioactive decay.

b) Cells may be damaged by nuclear fusion occurring within them.

c) Cells may be damaged by nuclear fission occurring within them.

d) Cells may be damaged by fast moving helium nuclei, electrons, or very high frequency photons.

e) Cells may be damaged by the beta decay of .C146

32.1.2. What is the absorbed dose of fast neutrons (RBE = 9.5) that is biologically equivalent to 75 rad of slow neutrons (RBE = 2.0)?

a) 350 rad

b) 120 rad

c) 16 rad

d) 48 rad

e) 5.0 rad

Chapter 32: Ionizing Radiation, Nuclear Energy, & Elementary Particles

Section 2:Induced Nuclear Reactions

A nuclear reaction is said to occur whenever the incident nucleus,particle, or photon causes a change to occur in the target nucleus.

Nuclear Reaction vs Decay

Example 3 An Induced Nuclear Transmutation

An alpha particle strikes an aluminum nucleus. As a result,and unknown nucleus and a neutron are produced.

n X D He 10

2713

42 A

Z

P3015

An induced nuclear reaction in whichuranium is transmuted into plutonium.

Induced Nuclear Reaction

32.2.1. Consider the following nuclear reaction: . The symbol “d” indicates a deuterium nucleus . Which one of the following statements is true concerning particle X in this reaction?

a) X must be an alpha particle.

b) X must be a photon.

c) X must be two protons.

d) X must be two neutrons.

e) X must also be a deuterium nucleus.

I , Te 12453

12252 dXH2

1

32.2.2. Consider the following nuclear reaction: . Which one of the following statements is true concerning particle X in this reaction?

a) X must be an alpha particle.

b) X must be a photon.

c) X must be a proton.

d) X must be a neutron.

e) X must be an electron.

24 He + 5

10B 613C + X

Chapter 32: Ionizing Radiation, Nuclear Energy, & Elementary Particles

Section 3:Nuclear Fission

A slowly moving neutron causes the uranium nucleus to fissioninto barium, krypton, and three neutrons.

Nuclear Fission

Conceptual Example 5 Thermal Neutrons Versus ThermalProtons or Alpha Particles

Why is it possible for a thermal neutron to penetrate a nucleus, whereasa proton or alpha particle would need a much larger amount of energy?

Neutron has not electromagnetic repulsion

A chain reaction

In a controlled chain reaction,only one neutron, on average,causes another neutron to fission.

Chain Reaction

32.3.1. In the process known as nuclear fission, which of the following occurs?

a) Two nuclei with atomic numbers less than that of iron are combined.

b) Two nuclei with atomic numbers greater than that of iron are combined.

c) A nucleus with an atomic number less than that of iron is split.

d) A nucleus with an atomic number greater than that of iron is split.

e) A nucleus with an atomic number much greater than that of iron is split by an alpha particle or a very low frequency photon.

32.3.2. Consider the following nuclear reaction:

What is X in this reaction?

a)

b)

c)

d)

e)

235 90 192 36 0U + X + Kr + 3 n.

Cs13855

La13957

La14057

Ba14256

Ba14156

32.3.3. How many neutrons are released in the following reaction:

a) 1

b) 3

c) 6

d) 8

e) 12

235 1 88 136 192 0 38 54 0U + n Sr + Xe + __ n?

32.3.4. How much energy is released in the following reaction:

a) 78.2 MeV

b) 96.1 MeV

c) 126.5 MeV

d) 140.8 MeV

e) 177.9 MeV

n? 21 + Xe+ Sr n + U 10

13654

8838

10

23592

32.3.5. Why is it that neutrons induce nuclear fission reactions better than protons do?

a) The nucleus exerts a repulsive force on the proton, but not on the neutron.

b) With more mass, neutrons have greater momentum than protons.

c) It is difficult to produce enough protons for the reaction to occur.

d) Neutrons experience the attractive strong nuclear force, whereas protons do not experience this force.

32.3.6. Which one of the following quantities is not necessarily conserved in nuclear reactions?

a) number of protons

b) electric charge

c) angular momentum

d) linear momentum

e) number of protons and neutrons

32.3.7.What is the origin of the energy that is released in a nuclear fission process?

a) electrostatic repulsion of neutrons

b) weak nuclear force

c) Coulomb energy of protons and electrons

d) electrostatic repulsion of protons

e) energy of the thermal neutrons

32.3.8. Which one of the following statements best explains why light nuclei do not undergo nuclear fission?

a) Light nuclei cannot be radioactive.

b) Light nuclei cannot absorb thermal neutrons.

c) Light nuclei do not have neutrons.

d) Light nuclei have a much higher binding energy than heavy nuclei.

e) Fission of a light nucleus would result in a reduction of the binding energy, rather than an increase.

Chapter 32: Ionizing Radiation, Nuclear Energy, & Elementary Particles

Section 4:Nuclear Reactors

A nuclear reactor consists of fuel elements, control rods, anda moderator.

Nuclear Reactors

The moderator slows neutrons and the control rods absorb neutrons.

Nuclear Reactors

32.4.1. Which one of the following statements concerning a nuclear reactor is true?

a) Nuclear energy is converted to thermal energy within the reactor.

b) Binding energy is converted to nuclear energy within the reactor.

c) Binding energy is created within the reactor.

d) Thermal energy is converted to nuclear energy within the reactor.

e) Energy is created in the fission reactions that occur within the reactor.

32.4.2. What is the purpose of the moderator in a fission reactor?

a) The moderator prevents heat loss from the reactor core.

b) The moderator decreases the speed of fast neutrons.

c) The moderator absorbs slow neutrons.

d) The moderator absorbs gamma rays.

e) The moderator prevents the reactor from reaching a critical state.

32.4.3. A nuclear power plant is constructed to generate 6.0 × 108 W. If the nuclear fission reaction used in the reactor produces 150 MeV per fission, how many fissions per second are required?

a) 6.0 × 1023

b) 2.5 × 1019

c) 6.4 × 1018

d) 1.1 × 1018

e) 4.0 × 1017

Chapter 32: Ionizing Radiation, Nuclear Energy, & Elementary Particles

Section 5:Nuclear Fusion

Two nuclei of very low mass can combine to generate energy. Thisprocess is called nuclear fusion.

Nuclear Fusion

Fusion

32.5.1. In a fusion reaction in which two helium nuclei are fused, what nucleus is produced?

a)

b)

c)

d)

e)

He42

Be64

C126

Li63

B85

Be84

32.5.2. Consider the following nuclear reaction: + X.

Identify particle X.

a) a photon

b) a proton

c) a neutron

d) an electron

e) No such particle is produced in this reaction.

He H H 42

31

21

32.5.3. Under what circumstances can a fusion reaction be self-sustaining?

a) Unlike fission, there are no circumstances in which fusion can be self-sustaining.

b) A fusion reaction can be self-sustaining if the reaction produces heavier nuclei from lighter nuclei.

c) A fusion reaction can be self-sustaining if the reaction produces lighter nuclei from heavier nuclei.

d) A fusion reaction can be self-sustaining if the reaction produces nuclei with larger binding energy per nucleon.

e) A fusion reaction can be self-sustaining if the reaction produces nuclei with smaller binding energy per nucleon

32.5.4. A certain fission reaction releases three neutrons. How many of these neutrons must go on to produce a subsequent fission if a chain reaction is to be sustained?

a) 1

b) 2

c) 3

d) It could be zero as long as there are other neutrons from other fission processes available.

32.5.5. Is there some minimum requirement of mass of fissile material, such as uranium, for a chain reaction to be sustained?

a) No, a small number of atoms is sufficient.

b) Yes, there must be enough material to prevent neutrons from escaping and defeating the chain reaction.

c) Yes, there must be enough fissions to continue the chain reaction.

d) Yes, there must be enough energy to continue the chain reaction.

Chapter 32: Ionizing Radiation, Nuclear Energy, & Elementary Particles

Section 6:Elementary Particles

Fundamental Particles This will be discussed in greater detail in Ch 32 3 Types of Fundamental Particles

Bosons (Messenger Particles) Photon, W+, W-, Z, Gluons Gravitons (?)

Leptons electron, tau, muon, and corresponding

neutrinos Quarks

up, down, charm, strange, top, bottom All particles have corresponding antiparticles

For particles with no charge, the particles is its own antiparticle

Mesons consist of a quark-antiquarkpair, while baryons consist of threequarks.

Elementary Particles - Hadrons

Elementary Particles - Hadrons

Mesons

Quark pairs

Pion ()

Kaon (K)

Eta ()

Baryons

3 quark combinations

Proton (p)

Neutron (n)

Lambda ()

Sigma ()

Omega ()

Pion production through p-p collision.

Particle Formation

Antiparticles, like positrons, can be used in positron emission tomography, or PET scans.

Uses of Particles

PET Scan Image

The current view of how matter is composed of basic units.

Units of Matter

32.6.1. In what way are photons related to charged particles, such as electrons and protons?

a) Photons, also having a charge, are members of the same family as other charged particles.

b) Charged particles, such as electrons and protons, interact with each other via photons.

c) Charged particles, such as electrons and protons, are composed of photons.

d) Photons interact with each other via charged particles, such as electrons and protons.

e) There is no relationship between these particles; and that is why photons have a family all to themselves.

32.6.2. Which one of the following kinds of particles is most closely related to an electron?

a) muon

b) quark

c) proton

d) kaon

e) neutrino

32.6.3. Which one of the following statements concerning the antiparticle of the proton is true?

a) The antiproton has a positive charge and a negative mass.

b) The antiproton has no charge and a positive mass.

c) The antiproton has a negative charge and a negative mass.

d) The antiproton has no charge and a negative mass.

e) The antiproton has a negative charge and a positive mass.

32.6.4. Within the theoretical framework called the Standard Model, which one of the following is not considered an elementary particle?

a) quark

b) electron

c) proton

d) antiquark

e) neutrino

32.6.5. Which one of the following particles is not composed of quarks?

a) proton

b) neutron

c) kaon

d) pion

e) muon

Chapter 32: Ionizing Radiation, Nuclear Energy, & Elementary Particles

Section 7:Cosmology

Hubble’s law Hdv

distance ofgalaxy from earth

speed of galaxy

year-lights

m022.0

H

Cosmology

Forces throughout BANG

32.7.1. The cosmic background radiation of the universe was produced at what point in the history of the universe?

a) a few billion years ago when the universe had cooled to about 3 K

b) about 12 billion years ago when the first atoms formed

c) after the first one hundred thousand years when protons, electrons, and neutrons were formed

d) after the first 1035 s

e) at the Big Bang

32.7.2. Which one of the following forces is the most difficult to unify with the other three fundamental forces?

a) weak nuclear force

b) strong nuclear force

c) electromagnetic force

d) gravitational force

e) normal force

32.7.3. Why is the gravitational force so difficult to reconcile with the other three fundamental forces into a single grand unified force?

a) It has infinite reach.

b) It is much weaker than the other forces.

c) It involves mass.

d) The universal gravitational constant cannot be accurately measured.

e) Gravitons have only been produced in small numbers in laboratories.