Describe the Geiger-Marsden scattering experiment.

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(N/A) In the Geiger-Marsden experiment,a beam of $5.5 \text{ MeV}$ $\alpha$-particles emitted from a ${ }_{83}^{214} \text{Bi}$ radioactive source is directed at a thin gold foil.
The $\alpha$-particles are collimated into a narrow beam by passing them through lead bricks.
This beam is allowed to strike a thin gold foil of thickness $2.1 \times 10^{-7} \text{ m}$.
The scattered $\alpha$-particles strike a fluorescent screen (typically $\text{ZnS}$),producing brief light flashes known as scintillations.
These scintillations are observed through a rotatable microscope,allowing the study of the number of scattered particles as a function of the scattering angle $\theta$.

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Given below are two statements:
$Statement$ $I$: Most of the mass of the atom and all its positive charge are concentrated in a tiny nucleus and the electrons revolve around it,is Rutherford's model.
$Statement$ $II$: An atom is a spherical cloud of positive charges with electrons embedded in it,is a special case of Rutherford's model.
In the light of the above statements,choose the most appropriate from the options given below.

The diagram shows the path of four $\alpha$-particles of the same energy being scattered by the nucleus of an atom. Which of these is/are not physically possible?

If the number of scattered alpha particles is $56$ at a scattering angle of ${90^o}$,then the number of scattered particles at a ${60^o}$ angle will be:

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Answer the following questions,which help you understand the difference between Thomson's model and Rutherford's model better.
$(a)$ Is the average angle of deflection of $\alpha$-particles by a thin gold foil predicted by Thomson's model much less,about the same,or much greater than that predicted by Rutherford's model?
$(b)$ Is the probability of backward scattering (i.e.,scattering of $\alpha$-particles at angles greater than $90^{\circ}$) predicted by Thomson's model much less,about the same,or much greater than that predicted by Rutherford's model?
$(c)$ Keeping other factors fixed,it is found experimentally that for small thickness $t$,the number of $\alpha$-particles scattered at moderate angles is proportional to $t$. What clue does this linear dependence on $t$ provide?
$(d)$ In which model is it completely wrong to ignore multiple scattering for the calculation of average angle of scattering of $\alpha$-particles by a thin foil?

The graph which depicts the results of the Rutherford gold foil experiment with $\alpha$-particles is:
$\theta$: Scattering angle
$Y$: Number of scattered $\alpha$-particles detected
(Plots are schematic and not to scale)

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