CAIE IGCSE Physics Brownian Motion Explanation
Practise explaining the irregular motion of smoke or pollen through uneven bombardment by rapidly and randomly moving gas or liquid particles.
- Syllabus
- 2026–2028
- Course
- Physics 0625
Exam points
- identify the visible specks as smoke or pollen particles rather than individual molecules
- state that fast, randomly moving fluid particles collide with the suspended particle
- explain its changing direction through unequal forces from uneven collisions on each side
2.1.2.5—And explain this motion (sometimes question 1
Fig. 4.1 shows apparatus used to observe the motion of smoke particles (Brownian motion).
Fig. 4.1
The glass cell has light shining on it from the side.
The smoke particles are seen as bright specks of light when looking through the microscope.
Explain, in terms of forces and the motion of air molecules, the cause of the motion of the smoke particles.
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