When smoke particles in a smoke cell are observed through a microscope, they are seen to move in a random, jerky fashion.
What is the explanation for this random movement?
The heat from the light source causes convection currents in the air.
The smoke particles are colliding with the walls of the container.
The smoke particles are being bombarded by tiny, fast-moving, invisible air molecules.
The smoke particles repel each other due to electrostatic forces.
151 exam-style questions on CIE IGCSE Physics 2.1.2a Particle structure and motion in solids, liquids and gases. Each one has a worked solution and a mark scheme showing where the marks go.