= Geiger-Marsden experiment
{c}
{wiki=Rutherford_scattering_experiments}
= Gold foil experiment
{synonym}
The Geiger-Marsden experiment probes the interior of a <chemical atom> by counting <alpha particles> deflected by metal foils. The surprising observation was a small population returning towards the incident side. <Hans Geiger> and <Ernest Marsden> performed the experiments under <Ernest Rutherford>'s direction; <Ernest Rutherford> developed the <Rutherford model> in 1911. Observation and interpretation were distinct contributions.<Dictionary of New Zealand Biography/Marsden, Ernest by Ross Galbreath>[Dictionary of New Zealand Biography; Biography, paragraphs on the 1909 undergraduate experiment and subsequent interpretation]{ref}
In 1909, a <radon> source and its <radioactive decay> products in a conical glass tube supplied <alpha particles> through a <mica> window towards a reflector. Lead shielded a fixed <zinc sulfide> screen from direct hits; an <optical microscope> resolved individual <particle scintillations>. Reflectors occupied the same position. Reflector-out counts tested air scattering; stacked <gold> foils and bare glass tested thickness and support contributions.<On a Diffuse Reflection of the Alpha-Particles by Hans Geiger and Ernest Marsden>[On a Diffuse Reflection of the α-Particles, printed pp. 495–498, Fig. 1 and experiments I–II]{ref}
Nearby source geometry blurred incidence <angles>. Extrapolating <platinum> counts uniformly over a <hemisphere> was an assumption, not a universal reflection probability.<On a Diffuse Reflection of the Alpha-Particles by Hans Geiger and Ernest Marsden>[Printed pp. 497, 499–500, angular limitation and experiment III]{ref}
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