Very small smoke particles suspended in air are observed through a microscope. They are seen to move in a rapid, random, and jerky motion (Brownian motion). What is the reason for this random movement?
The smoke particles are bombarded by randomly moving air molecules.
The smoke particles are carried by convection currents in the air.
The smoke particles are pushed by light rays reflecting off them.
The smoke particles are moved by the random vibration of their own atoms.
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.