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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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This page was last edited on 25 Juneat The distance from the center of the alpha particle to the center of the nucleus r min at this point is an upper limit for the nuclear radius, if it is evident from the experiment that the scattering process obeys the cross section formula given above. The microscope M and screen S were affixed to a rotating cylinder and could be moved a full circle around the foil so that they could count scintillations from every angle.

This model was devised by Lord Kelvin and further developed by J.

File:Experi~encia – Wikimedia Commons

Geiger placed a metal foil in the path of the rays at D and E to observe how the zone of flashes changed. Rutherfofd initial discovery was made by Hans Geiger and Ernest Marsden in when they performed the gold foil experiment in collaboration with Rutherford, in which they fired a beam of alpha particles helium nuclei at foils of gold leaf only a few atoms thick.

The alpha particles emitted from A was narrowed to a beam by a small circular hole at D. At one end of the tube was a quantity of ” radium emanation ” R that served as a source of alpha particles.

Foundational quantum physics Physics experiments in science Ernest Rutherford. Geiger pumped all the air out of the tube so that the alpha particles would be unobstructed, and they left a neat and tight image on the screen that corresponded rutherforrd the shape of the slit.


From Wikimedia Commons, the free media repository. At the other end of the tube was a fluorescent zinc sulfide screen S. They pointed the tube at the foil to see if the alpha particles would bounce off it and strike the screen on the other side of the plate, and observed an increase in the number of scintillations on the screen.

This time, they placed a small quantity of radium C bismuth on the lead rutyerford, which bounced off a platinum reflector R and onto the screen. From Ruthertord, the free encyclopedia.

Rutherford model and Rutherford-Bohr model. From this, Rutherford concluded that the majority of the mass was concentrated in a minute, positively-charged region the nucleus surrounded by electrons. Espalhamenot used a fluorescent screen to measure the trajectories of the particles.

File:Experi~encia rutherford.png

At the atomic scale, the concept of “solid matter” is meaningless, so the alpha particle would not bounce off the atom like a marble.

Scattering Foundational quantum physics Ernest Rutherford. If the plum-pudding model were correct, the positive “pudding”, being more spread out than in the correct model of a concentrated nucleuswould not be able to exert such large coulombic forces, and the alpha particles should only be deflected by small angles as they pass through.

It was then that I had the idea of an atom with a minute massive centre, carrying a charge.

At Rutherford’s behest, Geiger and Marsden performed a series of experiments where they pointed a beam of alpha particles at a thin foil of metal and measured the scattering pattern by using a fluorescent screen.


Most flew straight through the foil. This should have been impossible according to Thomson’s model; the alpha particles should have all gone straight through.

The disc could be rotated by means of a rod P to bring each window in front of the alpha particle source R. The astronomer Arthur Eddington called Rutherford’s discovery the most important scientific achievement since Democritus proposed the atom ages earlier. In an experiment where they shot a beam of alpha particles through hydrogen, the alpha particles knocked the hydrogen nuclei forwards in the direction of the beam, not backwards.

This puzzled Rutherford because he had espalhameto that alpha particles were just too heavy to be deflected so strongly. Rutherford asked Geiger to investigate just how much matter could scatter alpha rays. By using this site, you agree to the Terms of Use and Privacy Policy.

Media for cleanup for more information. If the alpha particle were to pass through a gold foil some atoms thick and rutheford maximal deflection in the same direction unlikelyit would still be a small deflection. It was almost as incredible as if you fired a inch ruthetford at a rutjerford of tissue paper and it came back and hit you.

This page was last edited on 2 Decemberat According to Coulomb’s Lawthe less concentrated a sphere of electric charge is, the weaker its electric field at its surface will be.