Rutherford Scattering Lab

The analytical probe models an alpha particle (Z=2) repelled by a stationary gold point charge (Z=79). Energy is the incident kinetic energy; the heavy target is treated as fixed. χ=2 atan(a/b), a=kZ₁Z₂e²/(2E), and rₘᵢₙ=a+√(a²+b²). The differential cross section is in barns per steradian (1 b=10⁻²⁸ m²). Atomic screening, target recoil, nuclear forces and quantum effects are omitted; this is not a complete gold-foil experiment.

Run draws a sampled batch. The circular beam samples b=bₘₐₓ√u and a uniform azimuth, so area is uniform. The planar strip samples signed b uniformly and has a different angular histogram; it is not a solid-angle cross section. The histogram counts only revealed trajectories in 5° bins, not dσ/dΩ. The random seed repeats the same batch. Sampling options are in the expandable menu.

Incoming asymptotes are parallel to +x. The display follows an exact repulsive Coulomb hyperbola, rotated to the incident beam, in a finite window; it is not a time animation of particles. b=0 turns back without a transverse displacement. Scale adapts to the chosen impact range and head-on turning distance; the target marker is symbolic. Drag to rotate and Ctrl/Meta+wheel to zoom; ordinary wheel scrolls the page. Pause, Resume and Reset control drawing. Hiding the browser pauses it.

The analytical probe updates directly. The drawing module loads only on Run; Reset or a changed input cancels a pending start. Only raw input drafts persist; no trajectories or camera settings are saved. The main toolbar holds energy, impact range and probe; trajectory count, beam distribution and random seed are in Sampling options.