Geiger–Marsden experiment

The Geiger–Marsden experiment (also called the Gold foil experiment or the Rutherford experiment) was a scientific experiment done by Hans Geiger and Ernest Marsden in 1909. They were instructed by Ernest Rutherford, and the experiment happened at the Physical Laboratories of the University of Manchester. The results of the experiment were surprising. They showed scientists that the atomic nucleus exists. This disproved the plum pudding model of the atom, and led to the Rutherford atomic model (also called the planetary model).

Geiger–Marsden Experiment Media

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  The "plum pudding model" of an atom with seven electrons, as imagined by J. J. Thomson in 1905

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  Left: Had Thomson's model been correct, all the alpha particles should have passed through the foil with minimal scattering.Right: What Geiger and Marsden observed was that a small fraction of the alpha particles experienced strong deflection.

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  In a cloud chamber, a 5.3 MeV alpha particle track from a 210Pb source (1) undergoes Rutherford scattering (2), deflecting by an angle of about 30°. It scatters once again (3), and finally comes to rest in the gas. The target nucleus recoils, leaving a short track (2). (cm scale)

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  This apparatus was described in a 1908 paper by Hans Geiger. It could only measure deflections of a few degrees.

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  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.

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  Schematic view of a head-on collision between an alpha particle and an atom. The radius of the atom is on the order of 10-10 m and the minimum stopping distance is on the order of 10-14 m.

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  Figure 1. Potential energy diagram for Rutherford's atom model illustrating concentration in the nucleus.

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  Figure 3 The basic components of the geometry of hyperbolas.