Fine smoke particles are trapped in a small glass container containing air. A bright light is shone into the container from the side.
When viewed from above through a microscope, tiny, bright specks of light are observed to move around in a random, jerky fashion.
What are the moving specks of light?
air molecules being bombarded by other air molecules
air molecules being bombarded by smoke particles
smoke particles being bombarded by air molecules
smoke particles being bombarded by other smoke particles
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.