Physics Unit 4
Unit 4: Revolutions in Modern Physics
In Unit 4, students examine observations of relative motion, light and matter that could not be explained by classical physics theories, and investigate how the shortcomings of existing theories led to the development of the special theory of relativity and the quantum theory of light and matter. The development of quantum theory and the theory of relativity fundamentally changed our understanding of how nature operates and led to the development of a wide range of new technologies, including those that revolutionised the storage, processing and communication of information. Students Definition of Evaluate the contribution of the quantum theory of light to the development of the quantum theory of the atom, and examine the Standard Model of particle physics and how it relates to the Big Bang theory.
Contexts that could be investigated in this unit include technologies such as GPS navigation, lasers, modern electric lighting, medical imaging, quantum computers and particle accelerators, and related areas of science such as space travel, the digital revolution and the greenhouse effect.
Participation in a range of experiments and investigations will allow students to apply their understanding of relativity, black-body radiation, wave–particle duality and the quantum theory of the atom to make and/or explain observations of a range of phenomena such as atomic emission and absorption spectra, the photoelectric effect, lasers and Earth’s energy balance.
Throughout the unit, students develop skills in planning and conducting investigations, interpreting results, synthesising evidence to support conclusions, recognising and defining the realm of validity of physical theories and models, and communicating these conclusions to others in a range of formats.
Unit Objectives
| 1. | Describe ideas and findings about special relativity, quantum theory and the Standard Model. |
| 2. | Apply understanding of special relativity, quantum theory and the Standard Model. |
| 3. | Analyse data about special relativity, quantum theory and the Standard Model. |
| 4. | Interpret evidence about special relativity, quantum theory and the Standard Model. |
| 5. | Evaluate processes, claims and conclusions about special relativity, quantum theory and the Standard Model. |
| 6. | Investigate phenomena associated with special relativity, quantum theory and the Standard Model. |
Subject Matter
Topic 1: Special Relativity (16 hours)
Science Understanding
The following subject matter can be assessed in the external assessment.
Special Relativity
- Describe observations of natural phenomena that cannot be explained by classical physics, e.g. the presence of muons in the atmosphere and the momentum of high speed particles in particle accelerators.
- Describe the concepts of frame of reference and inertial frame of reference.
- Definition of State the two postulates of special relativity.
- Explain how motion can only be measured relative to an observer.
- Explain the concept of simultaneity.
- Describe the consequences of the constant speed of light in a vacuum, e.g. time dilation and length contraction.
- Describe the concepts of time dilation, proper time interval, relativistic time interval, length contraction, proper length, relativistic length, rest mass and relativistic momentum.
- Describe the phenomena of time dilation and length contraction, including examples of experimental evidence of the phenomena.
- State the mass–energy equivalence relationship.
- Solve problems involving time dilations, length contraction and relativistic momentum use t= to√(1−v2c2), L=Lo√(1−v2c2), pv=mov√(1−v2c2) and ΔE= Δmc2.
- Explain the implications of relativistic momentum of objects increasing as they approach the speed of light.
- Explain paradoxical scenarios that may arise as a result of special relativity including the twins’ paradox, flashlights on a train, and the ladder in the barn paradox.
Science as a Human Endeavour (SHE)
The following subject matter may be assessed in the internal assessments.
- Appreciate the significant contributions of scientists such as Albert Einstein and Amalie ‘Emmy’ Noether who furthered our understanding of relativity.
- Explore how special relativity built upon the work of previous scientists and led to the development of relativistic theories of gravitation, mass–energy equivalence and quantum field theory.
- Explore how technologies such as satellites have dramatically increased the size, accuracy, and geographic and temporal scope of datasets with which scientists work.
- Explore how technologies such as GPS and Ring laser gyroscopes (RLG) assist with accurate navigation and consider the ethics surrounding their use.
- Explore how special relativity leads to the idea of mass–energy equivalence, which has subsequently been applied in nuclear fission reactors.
Science Inquiry
The following subject matter may be assessed in the internal assessments.
- Consider whether information could be transmitted at speeds faster than the speed of light.
- Consider the experimental evidence that supports the phenomena of time dilation and its real-world applications.
- Explore why the speed of light is the maximum possible speed in our universe.
Topic 2: Quantum Theory (16 hours)
Science Understanding
The following subject matter can be assessed in the external assessment.
Quantum Theory
- Explain how the double slit experiment provides evidence for the wave model of light.
- Describe light as an electromagnetic wave.
- Explain the concept of black-body radiation and the significance of the evidence it provides.
- Describe the photoelectric effect in terms of the photon.
- Describe the concepts of threshold frequency and work function.
- Solve problems involving blackbody radiation and the photoelectric effect using λmax=bT, E=hf=hcλ, Ek=hf−W,W=hf0.
- Compare the different models of the atom proposed by Rutherford and Bohr.
- Explain how Bohr’s model of the hydrogen atom integrates light quanta and atomic energy states to explain the specific wavelengths in the hydrogen line spectrum.
- Solve problems involving the line spectra of simple atoms using atomic energy states or atomic energy level diagrams using nλ=2πr, mvr=nh2π, 1λ=R(1n2f−1n2i) and λ=hp.
- Describe wave–particle duality of light by identifying evidence that supports the wave characteristics of light and evidence that supports the particle characteristics of light.
- Interpret data related to the photoelectric effect.
Science as a Human Endeavour (SHE)
The following subject matter may be assessed in the internal assessments.
- Appreciate the significant contributions of scientists such as Wilhelm Wien, Max Planck, Ernest Rutherford, Niels Bohr, Maria Goeppert-Mayer and Johannes Rydberg who furthered our understanding of quantum theory.
- Explore the historical development of the model of the atom in terms of traditional models.
- Consider how theories are contested, refined or replaced when new evidence challenges them, or when a new model or theory has greater explanatory power.
- Explore how the approximation of Earth as a black body can be used to predict climate patterns.
Science Inquiry
The following subject matter may be assessed in the internal assessments.
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Investigate variables related to the photoelectric effect such as
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photoelectron energy or velocity
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electrical potential difference across the anode and cathode
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wavelength or frequency of incident light
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work functions of surfaces.
Topic 3: The Standard Model (13 hours)
Science Understanding
The following subject matter can be assessed in the external assessment.
The Standard Model
- Describe the concepts of elementary particles and antiparticles.
- Definition of Identify the six types of quarks.
- Describe baryons and mesons.
- Identify the six types of leptons.
- Identify the four gauge bosons.
- Compare the strong nuclear, weak nuclear and electromagnetic forces in terms of the gauge bosons.
- Contrast the fundamental forces experienced by quarks and leptons.
Particle Interactions
- Describe the concepts of lepton number and baryon number.
- Solve problems relating to the conservation of lepton number and baryon number in particle interactions using B=nb−n−b, B=13(nq−n−q) and L=nl−n−l.
- Describe electron/electron, electron/positron and neutron decay interactions using particle interaction diagrams.
- Describe how symmetry in particle interactions occurs to maintain the principles of conservation.
Science as a Human Endeavour (SHE)
The following subject matter may be assessed in the internal assessments.
- Appreciate the significant contributions of scientists such as Chien-Shiung Wu, Richard Feynman and Peter Higgs who furthered our understanding of particle physics and The Standard Model.
- Explore the history of particle physics models and theories through the development of particle accelerators and contributions from notable physicists.
- Appreciate that particle accelerators like the Australian Synchrotron and Large Hadron Collider are developed through multinational collaborations between science organisations and governments.
- Appreciate the contribution of Australian scientists to the discovery of the Higgs boson.
- Explore the evidence relating to the Standard Model that supports the Big Bang theory.
Science Inquiry
The following subject matter may be assessed in the internal assessments.
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Examine evidence supporting theories related to particle physics.
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