NCERT Example 12.1 - Atoms
Question: What is the distance of closest approach to the nucleus of a 7.7 MeV α-particle before it comes momentarily to rest and reverses its direction? (Take Z = 79 for gold.)
Answer: r0 ≈ **30 fm (3.0 × 10⁻¹⁴ m)**.
Full step-by-step NCERT solution with diagrams on Something by Zero.