What is Brownian Motion?

BROWNIAN MOTION

Introduction

One of the most asked question is- what is Brownian Motion? Brownian motion was first observed in 1827 by Brown, a botanist. The phenomenon of Brownian movement can be easily observed in a laboratory if a colloidal solution is examined under and ultramicroscope. As the direction of illumination is perpendicular to the axis of the microscope, the suspended particles in the solution look like bright illuminated spots.

 Is eliminated particles continuously move to and fro in a random haphazard way. The particles spin, rise, sink and rise again. The movement of the particles is continuous and spontaneous. This non-stop random and haphazard motion is perpetual and spontaneous.

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So, what is Brownian Motion? This non-stop, random and haphazard motion is called Brownian Motion.

According to Albert Einstein's theory of transitional Brownian Motion, the particles tend to diffuse into the medium in coyrse of time. Consequently, the diffusion coefficient must be related to the Brownian movement.

The diffusion can be calculated in two different ways:
1. From  the irregular motion of the suspended                  particles.
2. From the difference in osmotic pressure caused by      the difference in concentrations of the suspended        particles.

Now let's see that what are the properties of Brownian Motion or what are the essential features of Brownian Motion.

Essential Features 

1. In Brownian Motion, the motion of each particle is      completely irregular and random. No two particles      are found to execute the same motion.

2. In Brownian Motion, the motion is continuous and      takes place for ever.

3. In Brownian Motion, the smaller the particles                appear to be more agitated than the larger ones.

4. In Brownian Motion, the motion is independent of      the nature of the suspended particles. Two                      particles of the same weight and size move equally      fast at the same temperature.

5. In Brownian Motion, the motion becomes more            vigorous when the temperature is increased.

6. In Brownian Motion, the motion is more vigorous        conspicuous in a liquid of lower viscosity.

7. In Brownian Motion, the motion is not modified            due to the shaking of the containing vessel.

Basis of Brownian Motion 

Brownian Motion is due to the bombardment of the dispersed particles by molecules of the medium which are themselves in a state of continuous haphazard motion. When thr particles are sufficiently large, the forces due to molecular impact almost completely balance.

This is why Brownian Motion cannot be observed with particles of large size. But when the size of the particles is very small, each particle will be acted upon by a resultant unbalanced force and will consequently move in a haphazard manner in response to the magnitude and direction of this force.

In other words, the particles move in response to the molecules of the liquid in a completely haphazard manner. The motion of the molecules of a gas is similar to Brownian Motion of suspended particles in colloidal solution. Thus the laws of kinetic theory of gases are applicable to Brownian Motion.

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