Which phenomenon explains the capture of very small particles through erratic motion?

The correct choice is based on the concept of diffusion, which refers to the process of particles spreading out in space resulting from their random motion. In the context of air filtration, very small particles, such as those found in smoke or other fine particulates, can be captured by filters due to this erratic movement. As these particles move in an unpredictable manner, they may collide with larger particles or the filter media itself, allowing them to adhere to the surfaces within the filter.

Diffusion is particularly significant in the filtration of aerosols, where the impact of Brownian motion (the random motion of particles suspended in a fluid) heavily influences the behavior of small particles. Instead of moving in straight lines, these particles often change direction, increasing the likelihood of being trapped in the filter matrix.

The other options represent different physical processes: convection refers to the bulk movement of air or fluid that can carry particles with it; filtration describes the general process of separating particles from an air or fluid stream; and centrifugation involves separating substances based on density using rotational force. None of these processes effectively explain the behavior and capture of very small particles through random motion as diffusion does.