🎯 Rutherford scattering — an alpha particle bends around the gold nucleus

Aim an alpha particle at the nucleus. A wide miss barely bends; a near head-on approach is flung back. The deflection is set by the impact parameter, the alpha's energy and the nuclear charge.

Walkthrough 1 / 3

Step 1 — the atom is mostly empty space (faint sphere) with a tiny, dense nucleus at its centre.

Impact parameter b 8 fm

Alpha energy K 5.0 MeV

Nucleus Z 79

b = 8.0 fm · θ = 31°
K = 5.0 MeV · Z = 79 · d = 45 fm

small b → large θ (near head-on turnaround)
most alphas (large b) sail almost straight through

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