Topics Overview: electromagnetic waves, refraction and diffraction, two-source interference, atomic spectra and discrete electron energy levels, blackbody radiation, albedo and the greenhouse effect, Doppler effect and spectral shifts, stars (brightness, luminosity, HR diagrams, stellar mass and radius, stellar parallax) (all students); single slit and multi slit diffraction, diffraction gratings, Bohr model for hydrogen, Doppler formulas (exact), Compton scattering, photoelectric effect, special relativity (HL only).
Detailed list of IB syllabus understandings and related guiding questions
Suggested Future Physics Contexts: radio waves in astronomy and spacecraft communications; atmospheric refraction (example: NASA's EM Spectrum Series), spectroscopy (possible extension: resolution of telescopes and diffraction gratings), terraforming Mars, redshift, interstellar travel (distance units), Compton scatter telescopes and photoelectric astronomy (HL), time dilation in interstellar travel (HL).
Skills in the study of physics to be explicitly taught: Understand how to accurately measure light intensity to an appropriate level of precision. Construct and interpret graphs using logarithmic scales. Generate data from models and simulations. Identify and extract data from databases.
Possible labs/activities to facilitate development of skills: determining the refractive index of a mystery material (PhET Bending Light simulation), intensity-distance relationship for light, Young’s double slit experiment, determining the speed of sound from standing waves in pipes of varying length, Melde’s experiment (standing waves on strings) and/or frequency vs length of a guitar string, verifying the Stefan-Boltzmann law using the PhET Blackbody Spectrum simulation, astronomical database activities (e.g. constructing HR diagrams).
HL: determining the wavelength of light from a diffraction grating, verifying Planck’s constant using the PhET Photoelectric Effect simulation.
Linking questions that can be answered during this unit:
How can light be modelled as an electromagnetic wave?
How were X-rays discovered?
What are the similarities and differences between light and sound waves?
How are electromagnetic waves able to travel through a vacuum?
Why does the intensity of an electromagnetic wave decrease with distance according to the inverse square law?
What can an understanding of the results of Young’s double-slit experiment reveal about the nature of light?
How can emission spectra allow for the properties of stars to be deduced?
How do emission spectra provide information about observations of the cosmos?
How can the motion of electrons in the atom be modelled on planetary motion and in what ways does this model fail?
What other simplified models are relied upon to communicate the understanding of complex phenomena?
In what ways can an electrical circuit be described as a system like the Earth’s atmosphere or a heat engine?
What relevance do simple harmonic motion and resonance have to climate change?
How can greenhouse gases be modelled as simple harmonic oscillators?
How can the idea of resonance of gas molecules be used to model the greenhouse effect?
What limitations are there in using a resonance model to explain the greenhouse effect?
What physical explanation leads to the enhanced greenhouse effect?
How are waves used in technology to improve society?
How can the use of the Doppler effect for light be used to calculate speed?
How can the Doppler effect be utilised to measure the rotational speed of extended bodies?
How can observations of one physical quantity allow for the determination of another?
In which ways has technology helped to collect data from observations of distant stars?
Why does the intensity of an electromagnetic wave decrease with distance according to the inverse square law?
Where do inverse square law relationships appear in other areas of physics?
How can gas laws be used to model stars?
How are concepts of equilibrium and conservation applied to understand matter and motion from the smallest atom to the whole universe?
HR diagrams have been helpful in the classification of stars by finding patterns in their properties. Which other areas of physics use classification to help our understanding?
What gives rise to emission spectra and how can they be used to determine astronomical distances?
How can emission spectra be used to calculate the distances and velocities of celestial bodies?
How is the equilibrium state of a system, such as the Earth’s atmosphere or a star, determined?
How can the understanding of black-body radiation help determine the properties of stars?
What applications does the Stefan-Boltzmann law have in astrophysics and in the use of solar energy?
What measurements of a binary star system need to be made in order to determine the nature of the two stars?
How does conservation of angular momentum lead to the determination of the Bohr radius? (HL)
Under what circumstances does the Bohr model fail? (HL)
How is photon scattering off an electron similar to and how is it different from the collision of two solid balls? (HL)
Can the Bohr model help explain the photoelectric effect? (HL)
How did the explanation of the photoelectric effect lead to the falsification of the idea that light was purely a wave? (HL)
Why is Compton scattering more convincing evidence for the particle nature of light than that from the photoelectric effect? (HL)
How are equations of linear motion adapted in relativistic contexts? (HL)
Why is the equation for the Doppler effect for light so different from that for sound? (HL)
What happens if the speed of light is not much larger than the relative speed between the source and the observer? (HL)
Special relativity places a limit on the speed of light. What other limits exist in physics? (HL)