Which statement correctly explains the observations or the conclusions drawn about the molecules in the air?
The root-mean-square speed (crmsc_{\text{rms}}crms) of the smoke particles is equal to that of the air molecules because they are in thermal equilibrium.
The erratic, random movement of the smoke particles is caused by the continuous, random bombardment of air molecules.
The motion of the smoke particles is driven primarily by thermal convection currents produced by the light source used to illuminate the glass container.
The individual air molecules can be resolved and directly observed under the microscope as they collide with the smoke particles.
48 exam-style questions on AQA A Level Physics Thermal physics (A-level only), covering Thermal energy transfer (A-level only), Ideal gases (A-level only), and Molecular kinetic theory model (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.