Question

The closest distance an $\alpha$ particle emitted can reach to the nucleus of an an atom is called

• A. Bohr's number
• B. Distance of closest approach
• C. Atomic radius
• D. None of these

Answer 1

Answer: (B)

Distance of closest approach

At a certain distance $r_{\circ }$ from the nucleus, the $\alpha$-particle stops for a moment and then begins to retrace its path, ie, it is scattered through an angle of ${180}^{\circ }$. And hence, the distance $r_{\circ }$ is called the distance of closest approach.