Atoms and Nuclei: JEE Main 2026 Physics question

7.9 MeV $\alpha$-particle scatters from a target material of atomic number 79. From the given data the estimated diameter of nuclei of the target material is (approximately) ______ m. $\left[\frac{1}{4\pi\epsilon_0}=9\times10^{9}\ \mathrm{Nm^2/C^2}\text{ and electron charge}=1.6\times10^{-19}\ \mathrm{C}\right]$