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SingaporePhysics

Modern Physics

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do discrete atomic energy levels produce the characteristic line spectra of atoms?

Explain discrete energy levels in atoms, relate transitions to emitted or absorbed photon energies, and account for line emission and absorption spectra
A focused answer to the H2 Physics learning outcome on atomic energy levels. Discrete energy levels, the photon-transition relation hf = E_i - E_f, and how line emission and absorption spectra arise as evidence of quantisation.
8 min answer →

Why is the mass of a nucleus less than the sum of its parts, and how does this mass defect explain the energy released in fission and fusion?

Relate mass defect to binding energy through E = mc squared, interpret the binding-energy-per-nucleon curve, and explain energy release in fission and fusion
A focused answer to the H2 Physics learning outcome on nuclear binding energy. Mass defect and E = mc^2, binding energy per nucleon and its curve, and why fission of heavy nuclei and fusion of light nuclei both release energy.
9 min answer →

Why does the photoelectric effect demand a particle model of light, and how is it described quantitatively?

Describe the photoelectric effect, explain why it requires the photon model, and apply Einstein's photoelectric equation
A focused answer to the H2 Physics learning outcome on the photoelectric effect. The experimental observations, why classical wave theory fails, the photon model, Einstein's photoelectric equation, work function and threshold frequency.
9 min answer →

How does the random, spontaneous nature of radioactive decay lead to the exponential decay law and the idea of half-life?

Describe radioactive decay as a random spontaneous process, apply the exponential decay law and the decay constant, and relate it to half-life and activity
A focused answer to the H2 Physics learning outcome on radioactive decay. Decay as a random spontaneous process, the decay constant and activity, the exponential decay law, and the link between half-life and the decay constant.
8 min answer →

What evidence established the nuclear model of the atom, and how do we describe nuclides and nuclear reactions?

Describe the evidence for the nuclear atom, represent nuclides and isotopes, and balance nuclear reaction and decay equations
A focused answer to the H2 Physics learning outcome on the nuclear atom. The alpha-scattering evidence for a small dense nucleus, nuclide notation and isotopes, the alpha, beta and gamma emissions, and balancing nuclear equations.
8 min answer →

How can both light and matter exhibit wave and particle behaviour, and what evidence supports this duality?

Explain wave-particle duality, apply the de Broglie relation, and describe the experimental evidence such as electron diffraction
A focused answer to the H2 Physics learning outcome on wave-particle duality. The dual nature of light and matter, the de Broglie wavelength, electron diffraction evidence, and when wave or particle behaviour dominates.
8 min answer →