In a Geiger Marsden experiment, calculate the distance of closest approach to the nucleus of Z=80, when an `alpha`-particle of `8 MeV` energy impings om it before it comes momentarily to rest and reverses its direction.

Explanation

To solve the problem of calculating the distance of closest approach to the nucleus of an atom with atomic number \( Z = 80 \) when an alpha particle with energy \( 8 \, \text{MeV} \) approaches it, we will use the concept of electrostatic potential energy and the formula for the distance of closest approach in a Coulombic interaction.

### Step-by-Step Solution:

**Step 1: Convert Energy from MeV to Joules**

The energy of the alpha particle is given as \( 8 \, \text{MeV} \). We need to convert this energy into Joules.

...