Question SPM.1A.HL.TZ0.40

An alpha particle (${}_2{}^4\text{He}$) of initial energy 5.5 MeV moves towards the centre of a nucleus of gold‑197 (${}_{79}{}^{197}\text{Au}$).

What is the distance of closest approach of the alpha particle?

A.  1.0 × 10⁻¹³ m

B.  4.1 × 10⁻¹⁴ m

C.  2.1 × 10⁻¹⁴ m

D.  6.6 × 10⁻³³ m