Brownian motion sim
Smoke specks scatter the lamp's light, so they show as bright points; they jiggle about at random, never settling.
Brownian motion · covers the GCSE, IGCSE, O-Level topic
What the sim shows
Smoke specks scatter the lamp's light, so they show as bright points; they jiggle about at random, never settling. They are being hit by air molecules, far too small to see, moving fast in all directions (about 463 m/s at 20 °C). At any moment more hit one side of a speck than the other, so it is pushed first one way and then another. This is evidence that air is made of tiny particles in constant, random motion. A smaller speck is knocked about more: a 1 µm speck wanders about 10 µm in a second, a 0.5 µm one about 14 µm. The paths are random walks worked out from the air's temperature and viscosity.
- The tracked speck's path
- Right: the view down the microscope
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
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