Rutherford Scattering Simulator
How to use the Rutherford scattering simulator
- Alpha particles stream in from the left towards a gold nucleus. Most pass almost straight through; the few aimed close to the nucleus swing sharply or bounce back.
- Count the deflections as they build up. Raise the energy and fewer bounce back; raise the nuclear charge and more do.
- Drag on the picture to turn it, scroll or pinch to zoom, and drag with the right button (or two fingers) to move it. Pause stops the clock; Reset starts the simulation again with the current settings.
Frequently asked questions
What did the gold foil experiment show?
In 1909 Geiger and Marsden, working for Rutherford, fired alpha particles at gold foil. About 1 in 8,000 came back towards the source, which was impossible if the atom's positive charge was spread out. Rutherford concluded that it is concentrated in a tiny, heavy nucleus.
Why do most particles go straight through?
The nucleus is about 10⁻¹⁴ m across while the atom is 10⁻¹⁰ m, so almost all alpha particles pass far enough away that the Coulomb repulsion barely deflects them. Only a particle aimed within a few nuclear radii is turned through a large angle.
What does the simulation calculate?
Each particle feels the Coulomb force kZe·2e ÷ r² from the nucleus and its path is stepped forward in time. The distance of closest approach for a head-on particle is 2kZe² ÷ E, so higher energy gets closer and nuclei with more charge deflect more.
It says WebGL is turned off.
The 3D view needs WebGL, which every current browser has. It can be switched off by hardware acceleration being disabled in the browser settings, or by a very old graphics driver. Turn hardware acceleration on, or try another browser.
Is anything uploaded?
No. The simulation is drawn by your own browser with WebGL; nothing is sent anywhere, and it keeps working offline once the page has loaded.