A beam of $\alpha$-particles is directed at a thin gold foil. One $\alpha$-particle has a head-on collision with a gold nucleus and is sent back along its original path. Which statement could account for the gold nucleus having a recoil speed that is small compared with the recoil speed of the $\alpha$-particle?
- AMost $\alpha$-particles are only slightly deflected as they pass through the gold foil.
- BThe $\alpha$-particle and the gold nucleus repel each other.
- CThe mass of the gold nucleus is much greater than the mass of the $\alpha$-particle.
- DThe momentum of the $\alpha$-particle decreases as it approaches the gold nucleus.