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Starter track

Follow the authored sequence, or switch to recap mode for a faster review of the same path.

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Starter track5 concepts3 checkpoints150 min

Modern Physics

Not started

Follow the bounded modern-physics branch from threshold emission into line spectra, matter waves, the Bohr hydrogen model, and half-life so the new concept set reads like one path instead of five isolated pages.

Use this track when the new modern-physics pages already in the catalog should feel like one coherent evidence chain. The path starts with threshold emission on the photoelectric bench, keeps discrete line patterns tied to one ladder-and-spectrum view, adds de Broglie's momentum-to-wavelength bridge before specializing that evidence into the Bohr hydrogen model, and then closes on radioactivity and half-life where single-event chance and large-sample regularity stay visible on one compact decay bench.

Threshold frequencyDiscrete spectral linesMatter wavelengthHydrogen seriesHalf-life curves

Entry diagnostic

Decide where to enter this path without opening a second testing system.

Reuse the photoelectric quick test, the existing spectra line-pattern challenge, and the matter-wave loop-fit challenge to decide whether to start from threshold emission or jump straight into the hydrogen model.

Start from beginning0 / 3 probes ready

Check the modern-physics evidence chain first

Start from beginning

No saved diagnostic checks are available yet, so the opening concept is still the best place to start.

Uses the same local-first quick tests, checkpoint challenges, and track history already saved in this browser.

Begin with Photoelectric Effect
  1. Quick testNot started4 questions

    Photoelectric quick test

    Check whether threshold frequency, brightness, and stopping-potential language already stay separate on the live emission bench.

    No saved quick-test result yet.

    Photoelectric effect
    Open Photoelectric Effect quick test
  2. ChallengeNot started7 checks

    Line-pattern checkpoint

    Use the spectra challenge to confirm that allowed level gaps still map cleanly onto a bounded visible-line pattern before the branch moves into matter waves.

    No saved checkpoint attempt yet.

    Atomic spectra
    Open Keep only two visible emission lines
  3. ChallengeNot started6 checks

    Matter-wave fit checkpoint

    Use the loop-fit challenge to verify that momentum, wavelength, and whole-number fits already stay connected before you skip into Bohr's hydrogen model.

    No saved checkpoint attempt yet.

    Matter waves
    Open Find the one-fit electron

Why this order

The sequence is authored to keep the model honest.

Photoelectric Effect comes first because the branch begins with the compact light-versus-threshold clue that brightness alone is not enough. Atomic Spectra follows by turning that same light story into discrete line evidence. de Broglie Matter Waves then bridges the catalog's wavelength language into quantized whole-number fits, so the Bohr Model arrives as a bounded hydrogen follow-up instead of a detached historical orbit story. Radioactivity and Half-Life closes the path by widening modern physics from quantized structure to probabilistic decay while still keeping the bench compact and conceptually honest.

Shared concept pages

Each step opens the same simulation-first framework.

Compare mode, prediction mode, quick test, worked examples, guided overlays, challenge mode, and read-next cues stay on the concept pages. The track only decides the guided order and the next recommended stop.

Guided path

Follow the concepts and checkpoint moments in order.

Checkpoint cards reuse the authored challenge entries already living on the concept pages.

  1. 1Not startedMastery: NewStart here

    Photoelectric Effect

    Use one compact lamp-to-metal bench to see why light frequency sets electron emission, why intensity alone fails below threshold, and how stopping potential reads the electron energy honestly.

    Start here before moving into Atomic Spectra.

    Modern PhysicsIntermediate30 min
    Start concept
  2. 2Not startedMastery: New

    Atomic Spectra

    Link discrete emission and absorption lines to allowed energy-level gaps with one compact ladder-and-spectrum bench that keeps transitions, wavelengths, and mode changes tied together.

    Builds on Photoelectric Effect before setting up de Broglie Matter Waves.

    Modern PhysicsIntermediate30 min
    Open concept
  3. Checkpoint 1LockedNot started

    Threshold-to-line checkpoint

    Carry the threshold story into a bounded spectrum where only two visible emission lines survive, so discrete wavelengths stay tied to the same modern-physics turn instead of becoming a separate shelf.

    Finish Atomic Spectra first. This checkpoint ties together Photoelectric effect and Atomic spectra through Keep only two visible emission lines.

    Pause here after Atomic Spectra before moving into de Broglie Matter Waves.

    Photoelectric effectAtomic spectra7 checksCoreGraph-linkedGuided start
    Return to Atomic spectraOpen concept
  4. 3Not startedMastery: New

    de Broglie Matter Waves

    Use one compact matter-wave bench to see how particle momentum sets wavelength, why heavier or faster particles get shorter wavelengths, and how whole-number loop fits form a bounded bridge toward early quantum behavior.

    Builds on Atomic Spectra before setting up Bohr Model.

    Modern PhysicsIntermediate30 min
    Open concept
  5. Checkpoint 2LockedNot started

    Matter-wave fit checkpoint

    Tune the loop until one wavelength fits cleanly, so the bridge from discrete line evidence into whole-number matter-wave fits is secure before the hydrogen model takes over.

    Finish de Broglie Matter Waves first. This checkpoint ties together Atomic spectra and Matter waves through Find the one-fit electron.

    Pause here after de Broglie Matter Waves before moving into Bohr Model.

    Atomic spectraMatter waves6 checksCoreGraph-linkedGuided start
    Return to Matter wavesOpen concept
  6. 4Not startedMastery: New

    Bohr Model

    Use a compact hydrogen bench to connect quantized energy levels, allowed transitions, and named spectral-line series while staying clear that Bohr is a useful historical model rather than the final quantum description.

    Builds on de Broglie Matter Waves before setting up Radioactivity and Half-Life.

    Modern PhysicsIntermediate30 min
    Open concept
  7. 5Not startedMastery: New

    Radioactivity and Half-Life

    Use one compact decay bench to see why each nucleus decays unpredictably, why large samples still follow a regular half-life curve, and how to read remaining-count graphs honestly.

    Capstone step after Bohr Model.

    Modern PhysicsIntermediate30 min
    Open concept
  8. Checkpoint 3LockedNot started

    Chance-versus-curve checkpoint

    Close the track by landing near one half-life so the expected smooth halving and the live noisy sample stay visible together instead of splitting modern physics into separate structure and decay stories.

    Finish Radioactivity and Half-Life first. This checkpoint ties together Bohr model and Half-life through Land on the one-half-life checkpoint.

    Final checkpoint that closes the authored track after Radioactivity and Half-Life.

    Bohr modelHalf-life8 checksCoreGraph-linkedGuided start
    Return to Half-lifeOpen concept