Tyndall Effect and Properties of Colloids

Tyndall effect is a scientific phenomenon that portrays the scattering of light when it’s passed through a colloidal solution. It helps conclude whether the solution is a true solution or a colloid solution. This effect has been named after an Irish Physicist John Tyndall, who proved this phenomenon in 1869.

Define Tyndall Effect 

In simple words, the Tyndall effect makes the path visible when a beam of light is passed through a colloidal solution and not when it is passed through a true solution. This is because the particles of the colloidal solution are comparable to the wavelength of the light beam. As a result, the beam of light is scattered, and its trajectory becomes visible through the solution. This phenomenon of scattering of light, when passed through the colloidal solution, is known as Tyndall Effect.

On the contrary, true solutions don’t scatter the light compared to colloidal solutions, and no Tyndall Effect can be observed. The reason behind this is that the constituent particles of the true solution are tinier than the required wavelength (1nm) for the scattering effect. Hence, this way, both the solutions can be easily differentiated through the Tyndall effect.

What causes the Tyndall effect? 

The light cannot travel straight through the colloidal solution’s scattered particles (like fog and smoke). Instead, it collides with these particles and spreads in all directions. It causes the effect of the trajectory of a light beam. It makes the path of the light visible through the solution or medium. And thus, the Tyndall effect is observed. 

Properties of Colloids: 

A colloid is a mixture containing particles between sizes 1-100 nm. It’s a heterogeneous mixture with particles denser than a solution to let a beam of light pass through it. Colloids make a path visible when a light beam is passed through it due to a phenomenon known as Tyndall Effect. Mixtures such as smoke and sunlight are examples of colloids. 

Here are its properties that differentiate it from true solutions and suspensions.

Heterogeneous Mixture:

As a mixture, a colloid consists of two mediums; a dispersed medium and a dispersion medium.

Stable nature:

The particles of colloids constantly remain in motion. Only a few colloid particles with larger sizes get sedimented slowly after a period.

Filterability:

The particles present in colloidal solution are minute enough to pass through ordinary filter papers but can be retained by membranes such as animal membrane, cellophane membrane, and ultrafilters.

Colour:

The colloidal particles present in the colloidal solution determine the solution’s colour. Light of longer wavelength is absorbed by large particles and hence transmits light of shorter wavelength and vice versa.

Colloidal solutions also show certain other unique effects like:

• Brownian Motion

• Electro-osmosis

Examples of Tyndall Effect 

The Tyndall effect has many examples that can be observed in our surroundings if looked closely. Some of them are mentioned below.

• Usually, it’s essential to turn on the dipper lights of cars and vehicles at night and early morning in winters due to dense fog. In such foggy weather, the car’s lights scatter through the fog and pave the way for light. That’s the practical example of the Tyndall Effect.

• The Tyndall effect is also responsible for the blue eyes. As blue has a shorter wavelength comparatively, it is scattered greatly. Also, low melanin causes the iris to be translucent. As a result, the light scatters highly and portrays blue colour on the retina.

• Sunlight passing through dense forests is also due to the Tyndall effect. Particles present in water mists work as a medium for the dispersion of light.

• Movie theatres also use the concept of the Tyndall effect to display light from a projector on the big screen.

Conclusion

The Tyndall effect is the phenomenon of scattering of light by colloidal solutions based upon the density of the solution. It makes the path visible through the mixture. 

The Tyndall effect is mainly responsible for the blue colour of the sky, scattering of light in fog and smoke and many similar events.

This study of the Tyndall effect by John Tyndall laid the foundation for many other discoveries in Physics. One of such discoveries is a new branch of science known as spectroscopy. It deals with understanding the properties of an unknown object through the Tyndall effect.