Brownian motion is the random motion of particles suspended in a medium. It is also known as pedesis. The particles subjected to Brownian motion tend to follow a zig-zag path of movement, which causes a partial or complete transfer of energy between them. The particle size is inversely proportional to the speed of motion. This means that smaller particles move faster than larger particles. Also, the momentum transfer is inversely proportional to the particle’s mass, which causes the smaller particles to gain more energy after the collision and move rapidly. Another factor that affects the Brownian motion of a particle is the viscosity of the fluid. The lower the viscosity of the solvent, the more will be the speed with which the particle moves. Some examples of Brownian motion include the motion of water molecules, the movement of dust particles, etc.
Examples of Brownian Motion
1. Motion of Pollen Grains in Still Water
The grains of pollen suspended in water move in a random fashion by bumping into each other, thereby exhibiting the Brownian movement. The collision of particles causes a significant change in momentum, which affects the speed with which the particles move. The first observation of the movement of the pollen grains in water was made in 1827 by a botanist called Robert Brown.
2. Movement of Dust Motes in a Room
The motion of dust particles is not normally visible; however, with the help of the Tyndall effect, the random movement of the dust motes can be observed easily. This random movement of the particles is a prominent example of Brownian motion in real life.
3. Molecules of Water
The movement of water molecules is unpredictable as they do not follow a particular pattern while moving. This random and haphazard fluctuation of the water molecules is yet another example of pedesis or Brownian Motion. The speed with which the water molecules exhibit Brownian Motion can be increased by increasing the temperature.
4. Diffusion of Calcium through Bones
Diffusion is the movement of a substance from an area of high concentration to a region of low concentration. The diffusion of calcium through the bones is one of the best examples of Brownian motion in real life. The bone-building in living organisms essentially require the absorption of calcium by the bones. The absorption of calcium particles takes place with the help of diffusion. Thereby, displaying Brownian motion in real life.
5. Movement of Holes of Electrical Charge in Semiconductors
When an electron leaves its original position and moves to the conduction band, it creates a void or an empty site in its initial position. This empty site is known as the hole and is positively charged. When an electron moves in a direction, the hole appears to be moving in the opposite direction. This movement of the electrons and holes is random in nature and denotes the Brownian motion.
6. Diffusion of Pollutants in the Air
The pollutants, gas molecules, dust motes, and other particles contained in the air exhibit the Brownian motion in one of the best possible manners. In this case, the air acts as the fluid, and the particles moving in it undergo energy transfer due to the continuous collision of the particles.
7. Plasma Particles in the Cell
Plasma particles present in a cell tend to undergo a number of chemical reactions including the collision between the charged and neutral particles, the elastic collision, inelastic collision, electron-ion collision, etc. This collision of the particles causes a transfer of energy and a change in momentum. The particles, therefore, exhibit Brownian motion.
8. Motion of Electrons in a Conductor
The motion of electrons in a conductor is purely random in nature as the electrons do not follow a strict path to move from one location to the other. This haphazard movement of the charged particles is yet another example of the Brownian motion. The Brownian movement exhibited by the electrons dies out when a potential is applied across the conductor. In such a case, the electrons get aligned and move in a single direction that is from lower potential to higher potential.