Physics 9702 · AS & A Level · Atoms, nuclei and radiation

Atoms, nuclei and radiation — practice question

In an experiment designed to show Brownian motion, smoke particles in a container are illuminated by a powerful light source and viewed through a microscope. The particles appear as tiny bright specks that are moving. What causes the Brownian motion?

  • Acollisions between the smoke particles and air molecules
  • Bcollisions between the smoke particles and the walls of the container
  • Cconvection currents within the air as it is warmed by the light source
  • Dkinetic energy gained by the smoke particles on absorption of light

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