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In Geiger-Marsden experiment, the number of scattered $\alpha$-particles $N(\theta)$ is plotted as a function of scattering angle $\theta$. Which of the following options represents the correct plot ?

This question was previously asked in
NEET UG Re-Exam 2026 Question Paper (21-Jun-2026)
The correct answer is

The Geiger-Marsden experiment, also known as the Rutherford gold foil experiment, was crucial in developing the nuclear model of the atom. In this experiment, α-particles were scattered by a thin foil of gold, and the scattering pattern was studied.

One of the key findings was the distribution of scattered α-particles with respect to the scattering angle θ. According to the Rutherford scattering formula, the number of α-particles scattered at an angle θ is inversely proportional to the fourth power of the sine of half the angle, given by:

\(N(\theta) \propto \frac{1}{\sin^4(\theta/2)}\)

This implies that as the scattering angle increases, the number of scattered α-particles decreases significantly. Therefore, the plot of \(N(\theta)\) as a function of θ should show a sharp decrease as θ increases.

Let's analyze the given options. The correct plot should depict the rapid decline of \(N(\theta)\) with increasing θ. Among the given options, the correct plot is:

This plot correctly captures the steep inverse relationship, showing that very few α-particles are scattered at larger angles, with most particles scattered at smaller angles.

In conclusion, the correct plot corresponds to the sharp decrease in the number of scattered α-particles as the scattering angle increases, which is consistent with the predictions of Rutherford's scattering formula.

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