Two α-particles with equal energies are fired towards the nucleus of a gold atom. Which diagram best represents their paths?

Question 6

Two α-particles with equal energies are fired towards the nucleus of a gold atom.

Which diagram best represents their paths?

Reference: Past Exam Paper – November 2005 Paper 1 Q39

Solution:

Answer: B.

  

The gold nucleus will cause a repulsive force on the alpha particles as they approach from any direction since they are all positively charged. [A is incorrect]

The gold nucleus would deflect the α-particles away from it (repulsive force). [D is incorrect] The closer the α-particle, the stronger is the repulsive force and thus, the deflection is larger. Thus, after being deflected, the paths of the alpha particles cannot remain parallel. [C is incorrect]