If an alpha particle with energy \( 7.7 \, \text{MeV} \) is bombarded on a thin gold foil, the closest distance from nucleus it can reach is ____________ \( \text{m} \). \( \text{(Atomic number of gold } = 79 \text{ and } \frac{1}{4 \pi \varepsilon_0} = 9 \times 10^{9} \text{ in SI units)} \)
