A Level Physics Practice Exam

Which fundamental force is responsible for electron capture?

1. Weak interaction

2. Strong interaction

3. Electromagnetic interaction

4. Gravitational interaction

The correct answer is: Weak interaction

The fundamental force responsible for electron capture is the weak interaction. This process occurs when a proton in a nucleus captures an orbiting electron and transforms into a neutron, emitting a neutrino in the process. The weak interaction is unique among the fundamental forces because it is the only force that can change the type of particle, allowing for the transformation of protons into neutrons and vice versa, which is essential for processes like beta decay and electron capture. In the context of the other forces, the strong interaction is primarily responsible for holding protons and neutrons together in the nucleus, while the electromagnetic interaction governs the behavior of charged particles, such as the attraction and repulsion of protons and electrons. The gravitational interaction, while pervasive, is negligible at the subatomic level compared to the other forces when it comes to particle interactions such as electron capture. Thus, the weak interaction is indeed the only force that facilitates this specific nucleon transformation.