An alpha particle and a deuterium ion are accelerated through the same potential difference. These are then directed towards a target nucleus to make…

Theoretical justification for same value of distance of closest approach $\displaystyle 2$ For a given nucleus, the distance of closest approach for a charged particle depends only on the accelerating potential difference. Since both \(\displaystyle \alpha\)-particle and a deuterium ion are accelerated through same potential difference, therefore distance of closest approach will be same for both.