Esses valores sao facilmente explicados ao verificar a dependencia da secao de choque com o angulo de espalhamento. Da expressao de Rutherford [Knoll. La introducción a la física moderna: Um ejemplo paradigmatico de cambio conceptual. O espalhamento Rutherford na sala de aula do ensino médio. A Física.

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Since the electrons are very light compared to the alpha particle, their influence can be neglected [6] and the atom can be seen as a heavy sphere of positive charge.

This was their alpha particle emitter.

The previous setup was unsuitable for doing this because the tube contained several radioactive substances radium plus its decay products and thus the alpha particles emitted had varying rangesand because it was difficult for them to ascertain at what rate the tube was emitting alpha particles. According to Coulomb’s Lawthe less concentrated a sphere of electric charge is, the weaker its electric field at its surface will be.

The differential cross section can be derived from espalhamnto equations of motion for a particle interacting with a central potential. Thomson’s model was not universally accepted even before Rutherford’s experiments.

Geiger–Marsden experiment

The astronomer Arthur Eddington called Rutherford’s discovery the most important scientific achievement since Democritus proposed the atom ages earlier. A microscope M was used to count the scintillations on the screen and measure their spread.

Geiger and Marsden covered the holes of the disc rutherfordd foils of gold, tin, silver, copper, and aluminum. He constructed a long glass tube, nearly two meters in length. I, the copyright holder of this work, hereby publish it under the following license:. From Wikimedia Commons, the free media repository.


Rutherford scattering was first referred to as Coulomb scattering because it relies only upon the static electric Coulomb potential, and the minimum distance between particles is set entirely by this potential.

From this, Rutherford concluded that the majority of the mass was concentrated in a minute, positively-charged region the nucleus surrounded by electrons. Media needing categories as of 14 February On this principle, Rutherford and Geiger designed a simple counting device which consisted of two electrodes in a glass tube.

Retrieved from ” https: It was quite the most incredible event that has ever happened to me in my life. Each impact of an alpha particle on the screen produced a tiny flash of light. The true radius is about 7. In a lecture Rutherford delivered at Cambridge Universityhe said:.

He had discovered the existence of alpha raysbeta raysand gamma raysand had proved that these were the consequence of the disintegration of atoms. If the collision causes one or the other of the constituents to become excited, or if new particles are created in the interaction, then the process is said to be ” inelastic scattering”. Accelerating charged particles radiate electromagnetic waves, so an electron orbiting an atomic nucleus in theory would spiral into the nucleus as it loses energy.

They noticed a few scintillations on the screen, because some alpha particles got around the plate by bouncing off air molecules. To fix this problem, scientists had to incorporate quantum mechanics into Rutherford’s model.


It was almost as incredible as if you fired a inch shell at a tutherford of tissue paper and it came back and hit you. If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file.


They measured each foil’s stopping power by equating it to an equivalent thickness of air. This page was last edited on 25 Juneat As a visual example, Figure 1 shows the deflection of an alpha particle by a nucleus in the gas of a cloud chamber.

Hantaro Nagaokawho had once proposed a Saturnian model of the atom, wrote to Rutherford from Tokyo in Rutherford model and Rutherford-Bohr model. For each metal, they then divided this number by the square of the atomic weight, and found that the ratios were more or less the same.

For example, electron scattering from the proton is described as Mott scattering[2] with a cross section that reduces to the Rutherford formula for non-relativistic electrons. The opposite espalhamennto of the tube was covered with a phosphorescent screen Z. Inhe was rutyerford to precisely ruttherford their charge-to-mass ratio.

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The tube was held on the opposite side of plate, such that the alpha particles it emitted could not directly strike the screen. The small size rutehrford the nucleus explained the small number of alpha particles that were repelled in this way. This puzzled Rutherford because he had thought that alpha particles were just too heavy to be deflected so strongly.

From Wikipedia, the free encyclopedia.