Atomic, nuclear and particle physics

14 hours


7.1 – Discrete energy and radioactivity


Essential idea: In the microscopic world energy is discrete.
Nature of science: Accidental discovery: Radioactivity was discovered by accident when Becquerel developed photographic film that had accidentally been exposed to radiation from radioactive rocks. The marks on the photographic film seen by Becquerel probably would not lead to anything further for most people. What Becquerel did was to correlate the presence of the marks with the presence of the radioactive rocks and investigate the situation further.
Understandings:
• Discrete energy and discrete energy levels Discharge tubes Concept
• Transitions between energy levels Models of the hydrogen atom The hydrogen atom (for real)
• Radioactive decay Alpha decay Beta decay Catching the neutrino
• Fundamental forces and their properties
• Alpha particles, beta particles and gamma rays Rutherford's Geiger-Marsden scattering experiment Rutherford scattering simulation
• Half-life
• Absorption characteristics of decay particles
• Isotopes Interactive periodic table including isotopes and half lifes
• Background radiation
Applications and skills:
• Describing the emission and absorption spectrum of common gases
• Solving problems involving atomic spectra, including calculating the wavelength of photons emitted during atomic transitions
• Completing decay equations for alpha and beta decay
• Determining the half-life of a nuclide from a decay curve
• Investigating half-life experimentally (or by simulation)
Guidance:
• Students will be required to solve problems on radioactive decay involving only integral numbers of half-lives
• Students will be expected to include the neutrino and antineutrino in beta decay equations
Data Booklet reference:
E = hf
l = hc / E
• The E represents the quantum of energy or the energy of a photon having a frequency f and a wavelength l. The speed of light in vacuum c = 3.00x108 m s-1. Planck's constant h = 6.63x10-34 J s.
International-mindedness:
• The geopolitics of the past 60+ years have been greatly influenced by the existence of nuclear weapons
Theory of knowledge:
• The role of luck/serendipity in successful scientific discovery is almost inevitably accompanied by a scientifically curious mind that will pursue the outcome of the “lucky” event. To what extent might scientific discoveries that have been described as being the result of luck actually be better described as being the result of reason or intuition?
Utilization:
• Knowledge of radioactivity, radioactive substances and the radioactive decay law are crucial in modern nuclear medicine
• How to deal with the radioactive output of nuclear decay is important in the debate over nuclear power stations (see Physics sub-topic 8.1)
• Carbon dating is used in providing evidence for evolution (see Biology sub-topic 5.1)
• Exponential functions (see Mathematical studies SL sub-topic 6.4; Mathematics HL sub-topic 2.4)
Aims:
Aim 8: the use of radioactive materials poses environmental dangers that must be addressed at all stages of research
Aim 9: the use of radioactive materials requires the development of safe experimental practices and methods for handling radioactive materials


7.2 – Nuclear reactions


Essential idea: Energy can be released in nuclear decays and reactions as a result of the relationship between mass and energy.
Nature of science: Patterns, trends and discrepancies: Graphs of binding energy per nucleon and of neutron number versus proton number reveal unmistakable patterns. This allows scientists to make predictions of isotope characteristics based on these graphs.
Understandings:
• The unified atomic mass unit
• Mass defect and nuclear binding energy Catching the neutrino
• Nuclear fission and nuclear fusion Balancing nuclear equations Nuclear fission
Applications and skills:
• Solving problems involving mass defect and binding energy
• Solving problems involving the energy released in radioactive decay, nu-clear fission and nuclear fusion
• Sketching and interpreting the general shape of the curve of average binding energy per nucleon against nucleon number
Guidance:
• Students must be able to calculate changes in terms of mass or binding energy
• Binding energy may be defined in terms of energy required to completely separate the nucleons or the energy released when a nucleus is formed from its nucleons
Data Booklet reference:
DE = Dm c2
• The DE represents the amount of energy that is equivalent to the mass defect Dm. The speed of light in vacuum c = 3.00x108 m s-1.
Theory of knowledge:
• The acceptance that mass and energy are equivalent was a major paradigm shift in physics. How have other paradigm shifts changed the direction of science? Have there been similar paradigm shifts in other areas of knowledge?
Utilization:
• Our understanding of the energetics of the nucleus has led to ways to produce electricity from nuclei but also to the development of very destructive weapons
• The chemistry of nuclear reactions (see Chemistry option sub-topics C.3 and C.7)
Aims:
Aim 5: some of the issues raised by the use of nuclear power transcend national boundaries and require the collaboration of scientists from many different nations
Aim 8: the development of nuclear power and nuclear weapons raises very serious moral and ethical questions: who should be allowed to possess nuclear power and nuclear weapons and who should make these decisions? There also serious environmental issues associated with the nu-clear waste of nuclear power plants.


7.3 – The structure of matter


Essential idea: It is believed that all the matter around us is made up of fundamental particles called quarks and leptons. It is known that matter has a hierarchical structure with quarks making up nucleons, nucleons making up nuclei, nuclei and electrons making up atoms and atoms making up molecules. In this hierarchical structure, the smallest scale is seen for quarks and leptons (10-18 m).
Nature of science: (1) Predictions: Our present understanding of matter is called the standard model, consisting of six quarks and six leptons. Quarks were postulated on a completely mathematical basis in order to explain patterns in properties of particles. (2) Collaboration: It was much later that large-scale collaborative experimentation led to the discovery of the predicted fundamental particles.
Understandings:
• Quarks, leptons and their antiparticles
• Hadrons, baryons and mesons The particle adventure LHC rap
• The conservation laws of charge, baryon number, lepton number and strangeness
• The nature and range of the strong nuclear force, weak nuclear force and electromagnetic force Epic rap battle between Einstein and Hawking.
• Exchange particles
• Feynman diagrams YouTube lesson on Feynman diagrams (beware switch of axes!)
• Confinement
• The Higgs boson Particle discovery timeline The elegant universe - NOVA
Applications and skills:
• Describing the Rutherford-Geiger-Marsden experiment that led to the discovery of the nucleus
• Applying conservation laws in particle reactions
• Describing protons and neutrons in terms of quarks
• Comparing the interaction strengths of the fundamental forces, including gravity
• Describing the mediation of the fundamental forces through exchange particles
• Sketching and interpreting simple Feynman diagrams
• Describing why free quarks are not observed
Guidance:
• A qualitative description of the standard model is required
Data Booklet reference:
Charge
Quarks
Baryon number
(2/3)e
u
c
t
1/3
-(1/3)e
d
s
b
1/3
All quarks have a strangeness number of 0 except the strange quark that has a strangeness number of -1

Charge
Leptons
-1e
e
m
t
0
n e
n m
n t
All leptons have a lepton number of 1 and antileptons have a lepton number of -1


Gravitational
Weak
Electromagnetic
Strong
Particles experiencing
All
Quarks, leptons
Charged
Quarks, gluons
Particles mediating
Graviton
W+, W-, Z0
g
Gluons
International-mindedness:
• Research into particle physics requires ever-increasing funding, leading to debates in governments and international research organizations on the fair allocation of precious financial resources
Theory of knowledge:
• Does the belief in the existence of fundamental particles mean that it is justifiable to see physics as being more important than other areas of knowledge?
Utilization:
• An understanding of particle physics is needed to determine the final fate of the universe (see Physics option sub-topics D.3 and D.4)
Aims:
Aim 1: the research that deals with the fundamental structure of matter is international in nature and is a challenging and stimulating adventure for those who take part
Aim 4: particle physics involves the analysis and evaluation of very large amounts of data
Aim 6: students could investigate the scattering angle of alpha particles as a function of the aiming error, or the minimum distance of approach as a function of the initial kinetic energy of the alpha particle
Aim 8: scientific and government organizations are asked if the funding for particle physics research could be spent on other research or social needs

TOPIC 7 PROBLEM SET

This is the complete problem set for Topic 7 - the same one I hand out. If you lose yours, you can download this one to replace it.




TOPIC 7 FORMATIVE ASSESSMENTS

These are the Formative Assessments (practice) that you will do in order to prepare yourself for the Summative Assessments (evidence of proficiency). You can expect to receive a mark of at least Proficient on the Summative Assessment if you understand everything on these Formative Assessments.




TOPIC 7 PROJECTS

Project marks are meant to replace summative assessment marks. Projects are your last opportunity to demonstrate your proficiency in meeting the standards of the assessment criteria.



EXTENSION NOTES FOR ENRICHMENT

Want to see the method of solving a differential equation? Really? Are you sure? Then view this document to see how it is done! Moo-ha-ha-ha.


The previous IB Physics cycle had Option J - Particle physics. Now IB thinks the stuff is important enough for the Core! The following PowerPoints have the stuff from the option that is not part of the Core material above. The following are all extensions of 7.3 - The structure of matter.

If you are interested in particle accelerators and detectors, and how stuff like the inside of protons and neutrons is explored, here you go.


If you are interested in quantum chromodynamics and are curious about the the color charge of quarks and how this creates the strong force, this slide show has more details. Art students will particularly feel at home here. Deep inelastic scattering tells how the inside of a proton is probed.


If you would like to see what kind of evidence there is for quarks and the standard model, run through this slide show. Believe it, or not!


How about taking a cursory look at the evolution of the universe from the Big Bang to the present? And maybe throw in a bit on string theory just to blow your mind...