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.

Author: Zulkir Arashishura
Country: Mali
Language: English (Spanish)
Genre: Sex
Published (Last): 12 September 2008
Pages: 75
PDF File Size: 3.26 Mb
ePub File Size: 20.23 Mb
ISBN: 728-8-33324-986-4
Downloads: 73901
Price: Free* [*Free Regsitration Required]
Uploader: Dir

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”. Both the negative and positive charges within the Thomson atom are spread out over the atom’s entire volume.

A microscope M was used to count the scintillations on the screen and measure their spread. This page was last edited on 25 June espaluamento, at Please help improve this media file by fspalhamento it to one or more categories, so it may be associated with related media files how?

As a visual example, Figure 1 shows the deflection of an alpha particle by a nucleus in the gas of a cloud chamber. It is a physical phenomenon explained by Ernest Rutherford in [1] that led to the development of the planetary Rutherford model of the atom and eventually the Bohr model.

The disc could be rotated by means esoalhamento a rod P to bring each window in front of the alpha particle source R. It was designed to accurately measure the scattering pattern of the alpha particles produced by the metal foil F.

At the other end of the tube was a fluorescent zinc sulfide screen S. When a positive alpha particle approached sufficiently close to the nucleus, it was repelled strongly enough to rebound at high angles. The timestamp is only as accurate as the clock in the camera, and it may be completely wrong.

File:Espalhamento com diferentes parâmetros de – Wikimedia Commons

From Wikipedia, the free encyclopedia. This too caused the patch of light on the screen to become more spread out.

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 to the shape of the slit. On this principle, Rutherford and Geiger designed a simple counting device which consisted of two electrodes in a glass rspalhamento. Geiger then allowed some air in the tube, and the glowing patch became more diffuse.


Rutherford scattering – Wikipedia

They spotted alpha particles bouncing off the metal foil in all directions, some right back at the source. The classical Rutherford scattering process of alpha particles against gold nuclei is an example of ” elastic scattering ” because neither the alpha particles nor the gold nuclei are internally excited. This time, they placed a small quantity of radium C bismuth on the lead plate, which bounced off a platinum reflector R and onto the screen. At one end was a bulb B containing “radium emanation” radon In their experiment, they prepared a small conical glass tube AB containing “radium emanation” radon”radium A” actual radiumand “radium C” bismuth ; its open end sealed with mica.

Geiger and Marsden covered the holes of the disc with foils of gold, tin, silver, copper, and aluminum. According to classical Newtonian physicsit was in fact impossible.

By using this site, you agree to the Terms of Use and Privacy Policy. The extension of low-energy Rutherford-type scattering to relativistic energies and particles that have intrinsic spin is beyond the scope of this article.

It would be affected only by the atom’s electric fields, and Thomson’s model predicted that the electric fields in an atom are too weak to affect a passing alpha particle much alpha particles tend to move very fast. In the middle of the tube was a 0. By using this site, you agree to the Terms of Use and Privacy Policy.

The alpha particles emitted from A was narrowed to a beam by a small circular hole at D. The above calculation is but an approximation of what happens when an alpha particle comes near espalhametno Thomson atom, but it is clear that the deflection at most will be in the order of a small fraction of a degree.

Since the electrons are very light rutherfofd to the alpha particle, their influence can be espzlhamento [6] and the atom can be seen as a heavy sphere of positive charge. Counting the scintillations, they observed that metals with higher atomic mass, such as gold, reflected more alpha particles than lighter ones such as aluminium.


The highly variable trajectories of the alpha particles meant that they did not all generate the same number of ions as they passed through the gas, thus producing erratic readings. The differential cross section can be derived from the equations of motion for a particle interacting with a central potential.

At the atomic scale, the concept of “solid matter” is meaningless, so the alpha particle would not bounce off the atom like a marble. Thomson himself was never able to develop a complete and stable model of his concept. The true radius is about 7.

Rutherford had discovered them in Geiger placed a metal foil in the path of the rays at D and E to observe how the zone of flashes changed. For the case of light alpha particles scattering off heavy nuclei, as in the experiment performed by Rutherford, the reduced mass is essentially the mass of the alpha particle and the nucleus off of which it scatters is essentially stationary in the lab frame.


The rotating disc in the center had six holes which could be covered with foil. 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.

They then set up a lead plate Pbehind which they placed a fluorescent screen S. Please link images File: Alpha particles are tiny, positively charged particles that are spontaneously emitted by certain substances such as uranium and radium. He constructed a long glass tube, nearly two meters in length.