Coaching Centre
Chapter 7: The Nature of Light Notes
HSC Physics Module 7: Maxwell's electromagnetic waves, measuring the speed of light, spectra and what starlight reveals, Newton's and Huygens' models, diffraction, interference and polarisation, black-body radiation and the photoelectric effect, and Einstein's special relativity from time dilation to E = mc².
Sections
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7A Maxwell and electromagnetic waves Mastered
How Maxwell unified electricity and magnetism, predicted electromagnetic waves and calculated their speed from two lab constants, how accelerating charges produce EM waves and how those waves propagate, and how Hertz confirmed it all.
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7B Measuring the speed of light Mastered
Historical and modern measurements of the speed of light, from Rømer's moons of Jupiter and Fizeau's toothed wheel to Foucault's rotating mirror, microwave cavities and lasers, and why c now defines the metre.
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7C Spectra and spectroscopy Mastered
Continuous, emission and absorption spectra and the conditions that produce them, how energy levels explain spectral lines, calculating photon energies, and using spectroscopy to identify elements.
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7D What starlight reveals Mastered
How a star's spectrum gives its surface temperature (Wien's law), chemical composition, motion towards or away from us (Doppler shift), rotation, and the density of its atmosphere and so its luminosity class.
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7E Newton and Huygens: particles or waves? Mastered
Newton's corpuscular model and Huygens' wave model of light, how each explained reflection and refraction, the evidence each side relied on, and the experiments by Young, Fresnel, Arago and Foucault that settled the argument in favour of waves.
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7F Diffraction and interference Mastered
Superposition and path difference, Young's double-slit experiment and d sin θ = mλ, fringe spacing, single-slit diffraction patterns, diffraction gratings and spectra, with an investigation to measure the wavelength of laser light.
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7G Polarisation Mastered
Polarised and unpolarised light, polarisation as evidence that light is a transverse wave, ways of polarising light, Malus's law I = Imax cos²θ, an investigation with a light sensor, and applications from sunglasses to phone screens.
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7H Black-body radiation and Planck's quanta Mastered
Black bodies and their radiation curves, Wien's displacement law, the failure of classical physics known as the ultraviolet catastrophe, and Planck's hypothesis that energy is quantised in units of E = hf.
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7I The photoelectric effect Mastered
The photoelectric effect, the observations that the wave model could not explain, Einstein's photon model and K = hf − φ, work function and threshold frequency, stopping voltage and the graph that measures Planck's constant, and photon momentum p = h/λ.
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7J Frames of reference and the aether Mastered
Inertial frames of reference and Galilean relativity, the problem Maxwell's constant c created, the aether and the Michelson–Morley experiment, Einstein's two postulates of special relativity and the evidence for them, and the relativity of simultaneity.
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7K Time dilation and length contraction Mastered
The light clock thought experiment, time dilation and proper time, length contraction and proper length, the Lorentz factor, and the experimental evidence from cosmic-ray muons, particle accelerators, atomic clocks flown around the world and GPS.
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7L Relativistic momentum and E = mc² Mastered
Why Newtonian momentum fails at high speeds, relativistic momentum and the cosmic speed limit, evidence from particle accelerators, and mass–energy equivalence E = mc² applied to rest energy, annihilation, nuclear reactions and the Sun.
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7M The Nature of Light: review Mastered
Module 7 review: a summary of the electromagnetic spectrum, wave model, quantum model and special relativity, all the formulas in one place, how the ideas connect, key words, and a mixed HSC-style test.