9478 / 2027

Chapter 19

Quantum Physics

Separate what is detected from the model used to predict it, and connect each equation to the quantity it describes.

Choose an appropriate quantum model, calculate particle and photon quantities, interpret probability graphs and explain discrete energy changes.

Photons and matter waves, normalised wavefunctions, amplitude superposition, localisation, the infinite square well and atomic line spectra. For 9478 (2027).

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Choose a topic

  1. Evidence for photons

    Explain threshold and wave evidence, then calculate photon energy, momentum and the meaning of intensity.

  2. Matter waves and detections

    Distinguish electron diffraction from accumulated single-particle interference and apply the de Broglie relation.

  3. Wavefunctions and probability

    Distinguish signed amplitude, density and interval probability, and normalise square and sinusoidal profiles.

  4. Adding probability amplitudes

    Add coherent amplitudes before squaring, interpret relative signs and connect superposition to allowed standing shapes.

  5. Localisation and momentum spread

    Explain why a localised state needs a spread of momenta and estimate the corresponding width scales.

  6. A particle in a box

    Use infinite-well boundary conditions to identify standing wavefunctions, nodes and allowed energies.

  7. Atomic transitions and spectra

    Connect discrete electronic levels and occupied initial states to emission, absorption and photon energy gaps.