Difference Between Tyndall Effect and Brownian Motion

Main Difference – Tyndall Effect vs Brownian Motion

Tyndall effect and Brownian motion are two concepts in chemistry which describe the behavior of particles in a substance. Tyndall effect explains the scattering of light when a light beam is passed through a particular substance. Brownian motion explains the movement of atoms or molecules or any other particles in a fluid. Both these effects can be observed using easy techniques. Tyndall effect can be observed by passing a light beam through a given substance. Brownian motion of large particles can be observed using a light microscope. The main difference between Tyndall effect and Brownian motion is that Tyndall effect occurs due to the scattering of light by individual particles whereas Brownian motion occurs due to the random motion of atoms or molecules in a fluid.

Key Areas Covered

1. What is Tyndall Effect
      – Definition, Explanation, Examples
2. What is Brownian Motion
      – Definition, Explanation, Examples
3. What is the Difference Between Tyndall Effect and Brownian Motion
      – Comparison of Key Differences

Key Terms: Brownian Motion, Colloid, Fluid, Opalescent Glass, Pollen Grains, Tyndall Effect

What is Tyndall Effect

Tyndall effect is the scattering of light as a light beam passes through a colloid. A colloid is a homogeneous mixture of particles that do not settle out. According to the theory of Tyndall effect, light is scattered by individual particles in the colloid. This effect was first discovered by a physicist named John Tyndall.

The degree of scattering depends on two factors: the frequency of the light beam and the density of the colloid. For example, red light has a higher wavelength and a lower frequency whereas blue light has a lower wavelength and a higher frequency. Colloidal solutions scatter blue lights stronger than red lights. This means shorter wavelengths are highly scattered. Longer wavelengths are transmitted through a colloid rather than scattering.

Figure 1: Opalescent Glass

Some examples for Tyndall effect include the visibility of headlights in fog, blue eye color, and opalescent glass. Opalescent glasses appear blue, but the light that passes through them appears orange due to the Tyndall effect.

What is Brownian Motion

Brownian motion is the random movement of particles in a fluid due to their collisions with other atoms or molecules. These particles can be observed as suspended particles in fluids due to Brownian motion. This was first discovered by a botanist named Robert Brown.

First observation of Brownian motion was the movement of pollen grains in water. The atoms or molecules in a fluid (liquid or gas) are tightly bound to each other due to weak bonds or attraction forces between them. Therefore, these particles (atoms or molecules) can move anywhere inside the boundary of the fluid. This movement is random. When pollen grains are added to water, the grains move here and there due to collisions with water molecules. Since water molecules are invisible and pollen grains are visible, the Brownian motion of these pollen grains can be observed using a light microscope.

Figure 2: Diffusion is an Example of Brownian Motion

The rate of Brownian motion depends on any factor that can affect the movement of particles in that fluid. Such factors are temperature and concentration. A common example of Brownian motion is the diffusion of a substance inside a fluid. Diffusion is the movement of particles from a region with a high concentration to a lower concentration.

Difference Between Tyndall Effect and Brownian Motion

Definition

Tyndall Effect: Tyndall effect is the scattering of light as a light beam passes through a colloidal solution.

Brownian Motion: Brownian motion is the random movement of particles in a fluid due to their collisions with other atoms or molecules.

Concept

Tyndall Effect: The concept of Tyndall effect describes the scattering of light by particles.

Brownian Motion:  The concept of Brownian motion describes the movement of particles inside a fluid due to collisions.

Observation

Tyndall Effect: Tyndall effect can be observed by passing a light beam through a substance.

Brownian Motion:  Brownian motion of macromolecules can be observed through a light microscope.

Factors Affecting the Effect

Tyndall Effect: Tyndall effect is affected by the frequency of the incident light beam and the density of particles.

Brownian Motion: Brownian motion is affected by any factor that affects the movement of particles inside a fluid, such as temperature and concentration.

Examples

Tyndall Effect:  Blue eye color is a good example of Tyndall effect.

Brownian Motion: Diffusion that takes place in solutions is a good example of Brownian motion.

Conclusion

Tyndall effect and Brownian motion can be used to explain the behavior of particles in a substance. These are easily observable effects. The main difference between Tyndall effect and Brownian motion is that Tyndall effect occurs due to the scattering of light by individual particles whereas Brownian motion occurs due to the random motion of atoms or molecules in a fluid.

References:

1. Helmenstine, Anne Marie. “Tyndall Effect Definition and Examples.” ThoughtCo, Feb. 11, 2017, Available here.
2. Helmenstine, Anne Marie. “An Introduction to Brownian Motion.” ThoughtCo, Mar. 15, 2017, Available here.
3. “Brownian motion.” Wikipedia, Wikimedia Foundation, 29 Oct. 2017, Available here.

Image Courtesy:

1. “Why is the sky blue” By optick – (CC BY-SA 2.0) via Commons Wikimedia
2. “Diffusion” By JrPol – Own work (CC BY 3.0) via Commons Wikimedia