It is the distance from nucleus at which an energetic a-particles approaching directly towards the nucleus, retraces its path through 180°. At distance of closest approach speed of a-particle is zero.
Class 12 Physics Chapter 12 Atoms Session 2024-2025.
Define the distance of closest approach.
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The distance of closest approach is the minimum distance between the nucleus and an incoming particle, such as an alpha particle, during a collision. At this point, the particle’s kinetic energy is completely converted into electrostatic potential energy due to the nucleus’s repulsion.
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