Gold foil experiment

[[Image:Rutherford gold foil experiment results.png|right|200px|thumb|Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed.

Methodology

Geiger and Marsden bombarded different metal foils with alpha particles generated from a tube of radium bromide gas. A low power microscope was used to count the scattering of these particles, a procedure requiring many hours in a darkened room watching for tiny flashes of light as the scattered particles struck a zinc sulphide scintillant screen.

Related Topics:
Alpha particle - Microscope - Zinc sulphide - Scintillant

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A variety of different foils were used such as aluminium, iron, gold and lead along with different thicknesses of gold foil made by packing several pieces of very thin foil together. Given the very high mass and momentum of an alpha particle, the expectation was that the particles would pass through having being deflected by a tiny angle at most, with the number of particles penetrating falling off as the thickness of foil (and the atomic weight of its material) was increased; the remainder being absorbed.

Related Topics:
Aluminium - Iron - Gold - Lead - Mass - Momentum

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

However they were astonished to find that although this was generally true, around 1 in 8000 particles were reflected through more than 90 degrees even with a single sheet of extremely thin, 6x10-8 metre (or about 200 atoms) thick, gold foil, an observation completely at odds with the predictions of the plum pudding model.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~