Electron Spin and the Stern-Gerlach Experiment · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Two spots, no smear

Science · Quantum & Modern Physics · ages 21-22
Name ______________________   Date ____________

  1. Why did two beams rule out a classical magnetic moment?

    • Classical moments always vanish
    • Classical moments tilt at any angle and would smear
    • Magnets cannot deflect atoms

  2. What pattern did the silver beam form?

    • A broad smear
    • Exactly two sharp beams
    • A single spot

  3. What are the allowed electron spin projections?

    • Any fraction
    • 0 and h bar
    • Plus or minus h bar over 2

  4. Fine structure is the tiny splitting of lines from spin orbit coupling.

    Circle one:   True   False

  5. Why silver atoms?

    • Each carries one unpaired electron whose spin decides the kick
    • Silver has no electrons
    • Silver melts magnets

  6. Each Bohr line turns out to be a close pair. What causes it?

    • Spin orbit coupling
    • Extra protons
    • Instrument noise

  7. A friend claims the two spots are just orbital m values of silver. What is wrong?

    • Silver orbital projections would give more than two tilts
    • Spin never affects magnets
    • Orbitals already explain everything

  8. Could you explain why the silver beam splits into two and not into a smear?

    • Orbital tilts are continuous
    • Only two spin settings exist, so only two deflections occur
    • The magnet has two poles
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Two spots, no smear W1-mt_HVFLoNe6wk-s1

  1. Classical moments tilt at any angle and would smear · Any tilt allowed means a continuum of deflections, which is a band and not two spots.
  2. Exactly two sharp beams · The lopsided magnet split the beam into two, revealing two magnetic settings.
  3. Plus or minus h bar over 2 · Spin one half allows only up and down along the chosen axis.
  4. True · Spin and orbital magnets tug on each other and shift levels by small amounts.
  5. Each carries one unpaired electron whose spin decides the kick · The lone outer spin dominates the atomic magnet that the field grabs.
  6. Spin orbit coupling · The coupling energy separates the line into close partners.
  7. Silver orbital projections would give more than two tilts · Orbital sets offer many projections, while the beam shows exactly two.
  8. Only two spin settings exist, so only two deflections occur · Two allowed magnetisms give two forces, hence two beams.
Worksheet · LightMySky