Editing Rutherford scattering experiments (section)

===Dependence on foil material and thickness: the 1910 experiment===
[[File:Geiger-1910-fig1.GIF|upright=1.5|thumb|This apparatus was described in 1910 paper by Geiger.  It was designed to precisely measure how the scattering varied according to the substance and thickness of the foil.]]
A 1910 paper<ref name=Geiger1910>[[#refGeiger1910|Geiger (1910)]]</ref> by Geiger, ''The Scattering of the α-Particles by Matter'', describes an experiment to measure how the most probable angle through which an alpha particle is deflected varies with the material it passes through, the thickness of the material, and the velocity of the alpha particles. He constructed an airtight glass tube from which the air was pumped out.  At one end was a bulb (B) containing "radium emanation" ([[radon]]-222).  By means of mercury, the radon in B was pumped up the narrow glass pipe whose end at A was plugged with [[mica]].  At the other end of the tube was a fluorescent [[zinc sulfide]] screen (S).  The microscope which he used to count the scintillations on the screen was affixed to a vertical millimetre scale with a vernier, which allowed Geiger to precisely measure where the flashes of light appeared on the screen and thus calculate the particles' angles of deflection. The alpha particles emitted from A was narrowed to a beam by a small circular hole at D.  Geiger placed a metal foil in the path of the rays at D and E to observe how the zone of flashes changed. He tested gold, tin, silver, copper, and aluminium. He could also vary the velocity of the alpha particles by placing extra sheets of mica or aluminium at A.<ref name=Geiger1910/>

From the measurements he took, Geiger came to the following conclusions:<ref name="BelyaevRoss2021"/>{{rp|5}}
* the most probable angle of deflection increases with the thickness of the material
* the most probable angle of deflection is proportional to the atomic mass of the substance
* the most probable angle of deflection decreases with the velocity of the alpha particles

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{{Anchor|1911_paper}}