Question

Brownian motion of smoke particles can be studied by using the apparatus shown below. To observe the motion, some smoke is enclosed in the smoke cell and then observed through the microscope as shown below

1. Explain the role of the smoke particles, lens and microscope in the experiment 
2. State and explain the nature of the observed motion of the smoke particles
3. State what will be observed about the motion of the smoke particles if the temperature surrounding the smoke cell is raised slightly

Answer 1

1. Smoke particles – smoke particles are larger than air molecules and light enough to move when bombarded by air molecules 
   Lens – focuses the light from the lamp on the smoke particles, causing them to be observable
   Microscope – enlarges/magnifies the smoke particles so that they are visible 
2. Smoke particles more randomly/zigzag 
   Air molecules bombard the smoke particles
   Air molecules are in random motion
3. The speed of motion of smoke particles will be observed to be lighter/faster/speed increases.

Answer 2

1.The role of the smoke particles is to show the behaviour of air molecules 
2.lens are used to focus the light from the lamp to the smoke cell making them visible
3.microscope enlarge the smoke particles so that they are visible