Physics 9702 · AS & A Level · Atoms, nuclei and radiation

Atoms, nuclei and radiation — practice question

When $\alpha$-particles are aimed at gold leaf 1 nearly all $\alpha$-particles travel straight through with no deflection, 2 a small number of $\alpha$-particles are scattered through large angles. What explains these observations?

  • A1 most $\alpha$-particles have enough energy to pass right through the gold leaf 2 gold is very dense so a few low energy $\alpha$-particles bounce back from the gold surface
  • B1 most $\alpha$-particles miss all gold atoms 2 a few $\alpha$-particles bounce off gold atoms
  • C1 the gold nucleus is very small so most $\alpha$-particles miss all nuclei 2 occasionally the path of an $\alpha$-particle is close to a nucleus
  • D1 the positive charge in an atom is not concentrated enough to deflect an $\alpha$-particle 2 occasionally an $\alpha$-particle experiences many small deflections in the same direction

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