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Question
In a beam of sunlight entering a room, we can sometimes see dust particles moving in a haphazard way in the air. Why do these dust particles move?
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Solution
When a beam of sunlight enters a room, suspended dust particles are seen moving haphazardly. This is because the dust particles are constantly hit by the fast moving particles of air and due to this remain suspended despite gravity acting on them. This is an example of Brownian motion.
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