Rutherford's gold foil experiment

In summary, Rutherford's experiment showed that the positive charge in an atom is concentrated in a heavy particle (nucleus) whereas the negative charge is concentrated in one-charge light electrons.
  • #1
johncena
131
1
Can anyone explain the experiment? i am having a big doubt in it.
 
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  • #2
Explain your doubt.
 
  • #3
negitron said:
Explain your doubt.

The OP is probably Indian and means doubt in the sense of 'question' rather than in the more-common (and western) usage of 'disbelief'.
 
  • #4
It doesn't matter; either way, it applies: what's the question, specifically? Sure, I can explain Rutherford's experiment, but without knowing what's giving the OP trouble, it's hard to know which aspect to focus on.
 
  • #5
First of all, if you write out the equations for Rutherford scattering of alpha particles from a point nuclear charge, you get an equation that has an angular dependence something like sin4(θ/2) (my memory fails a little). If it deviates from this at large angles, then the alpha particle is hitting something. I did this experiment in a physics lab many years ago, and my biggest problem was that the gold foil stuck to my fingers.

Erratum: It should read 1/sin4(θ/2) . See
http://en.wikipedia.org/wiki/Rutherford_scattering
 
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  • #6
When I was deriving the formula for scattering fast charged particles from atoms, I discovered that, due to motion around the atomic center of inertia, the positive charge in an atom is quantum mechanically smeared, just like the negative (electron) charge but localized in much smaller region. Thus the elastic cross section differs from the Rutherford formula at large angles. It can be observed in specially designed experiments.

By the way, in a solid state the nucleus QM de-localisation is as large as the lattice step so the elastic cross section differs essentially from the Rutherford formula at large angles. It is the inclusive cross section (elastic + inelastic ones) that is reduced to the Rutherford formula. Normally it is the inclusive cross section that is observed.
 
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  • #7
Bob S said:
First of all, if you write out the equations for Rutherford scattering of alpha particles from a point nuclear charge, you get an equation that has an angular dependence something like sin4(θ/2) (my memory fails a little). If it deviates from this at large angles, then the alpha particle is hitting something. I did this experiment in a physics lab many years ago, and my biggest problem was that the gold foil stuck to my fingers.

Oh sure. Whenever we do experiments with lead foil or aluminum foil there are no problems. But the second we use gold foil all the students suddenly get a case of very "sticky fingers" indeed...
 
  • #8
A thin gold foil contains infinite number of atoms.So, by passing alpha rays to this foil , how was Rutherford able to explain the structure of a single atom?
 
  • #9
johncena said:
A thin gold foil contains infinite number of atoms.So, by passing alpha rays to this foil , how was Rutherford able to explain the structure of a single atom?

He did not explain the structure of a single atom, he discovered that the positive charge is entirely concentrated in a heavy particle (nucleus) whereas the negative charge is concentrated in one-charge light electrons. The Rutherford model needed in fact QM to explain the atomic stability.
 
  • #10
johncena said:
A thin gold foil contains infinite number of atoms

No. In a thin gold foil the alpha particle might only need pass through several hundred atoms. If these atoms where more or less homogenious then we would expect that every alpha particle would interact with the foil in much the same way as every other alpha particle. But Rutherford instead observed that many alpha particles went straight through with little or no deflection yet a few were greatly deflected and some even rebounded (deflected more than 180 degrees). This provided very good evidence that the atoms were not homogenious and lead to the proposed model of a compact positive nucleus containing most of the mass in only a very small amount of the total atom volume.
 
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  • #11
johncena said:
A thin gold foil contains infinite number of atoms.So, by passing alpha rays to this foil , how was Rutherford able to explain the structure of a single atom?

The Rutherford (backward) scattering is also observed from a thick solid pieces. It is not possible without heavy nuclei. There is a strong Z- and M_a dependence of the scattered flux.
 

What was Rutherford's gold foil experiment?

Rutherford's gold foil experiment was a series of experiments conducted by Ernest Rutherford in 1910 to study the structure of the atom. It involved firing alpha particles at a thin sheet of gold foil and observing how they interacted with the atoms in the foil.

Why was Rutherford's gold foil experiment important?

Rutherford's gold foil experiment was important because it provided evidence for the existence of a small, dense, positively charged nucleus at the center of an atom. This disproved the previously accepted "plum pudding" model of the atom and paved the way for our current understanding of atomic structure.

How did Rutherford's gold foil experiment work?

Rutherford's gold foil experiment involved firing alpha particles (positively charged particles) at a thin sheet of gold foil. Most of the alpha particles went straight through the foil, but a small percentage were deflected at large angles or even bounced back. This showed that the positive charge of the atom was concentrated in a small, dense nucleus at the center.

What were the results of Rutherford's gold foil experiment?

The results of Rutherford's gold foil experiment showed that most of the alpha particles passed through the gold foil with minimal deflection, indicating that most of an atom is made up of empty space. However, a small percentage of alpha particles were deflected at large angles or even bounced back, which led to the discovery of the atomic nucleus.

What impact did Rutherford's gold foil experiment have on our understanding of the atom?

Rutherford's gold foil experiment had a major impact on our understanding of the atom. It provided evidence for the existence of a small, dense, positively charged nucleus at the center of an atom and disproved the previously accepted "plum pudding" model. This experiment also paved the way for further research and advancements in the field of atomic structure.

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