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For Students · Stern-Gerlach

Stern-Gerlach for a laser cavity

Built for students learning it for a class or exam. See the concept move instead of memorizing formulas — and check your homework intuition. Simulate a laser cavity live below — adjust the inputs and watch it respond, right in your browser.

Stern-Gerlach ExperimentLive

spin measurement & projection

Controls

Presets

Analyzer angle θ (°)

Speed1×

Atoms prepared spin-up are measured along an axis tilted by θ. Quantum mechanics says each atom randomly comes out up or down, with probability cos²(θ/2) for up — never a fraction. At 90° it is a perfect coin flip; at 180° it always flips. The running tally converges to the Born-rule probability.

▶ Run in Python

Data Inspector

P(up) theory0.750

Measured up0.0%

Atoms1

Governing equation

P (↑) = cos^{2} \frac{θ}{2} = 0.750, P (↓) = sin^{2} \frac{θ}{2} = 0.250, θ = 6 0^{\circ}

Reading this result: Tilted by 60°, the analyzer still favors up: theory predicts P(up) = cos²(θ/2) ≈ 0.75, and the tally converges there.

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Frequently asked questions

Is this good for students?: Yes — this version of "Stern-Gerlach for a laser cavity" is framed for students learning it for a class or exam. See the concept move instead of memorizing formulas — and check your homework intuition.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.