Tyndall effect - A light scattering phenomenon

Tyndall effect

What is the Tyndall effect?

When a strong beam of light is passed through a true solution, we cannot see the light unless the eye is placed in the path but when the same beam of light is passed through a sol it becomes visible. What happens in this case of a sol is that the light scatters from the surface of the colloidal particles and reaches our eyes. This phenomenon is called the Tyndall effect.

When a colloidal solution is observed from the same way it will appear clean/translucent but whenever we observe that solution from the right angle then it will surely show some or more opalescence. We should also know that when we view this path of light from the right angle then this light is illuminated by bluish light. Faraday first observed this effect and was further studied by Tyndall that’s why it is called Tyndall effect. Tyndall cone can also be observed which is the bright cone of light.

The path of the beam is illuminated by the scattering of light in the colloidal dispersion. If these two conditions are satisfied then we can observe the Tyndall effect:

  • When the diameter of the dispersed particles is little smaller than the wavelength of light used.
  • The refractive indices of the dispersion medium and the dispersed phase vary in magnitude to a large scale.

The wavelength of the light scattered by the dispersed particles determines the color of the colloidal solution.

Size and the nature of particles also plays an important role in determining the wavelength of light.

As we know that the mixture of milk and water appears blue when observed by the reflected light and appears red when observed by the transmitted light. After observing this we can say that the color of the colloidal solution varies with the change in receiving the light to the observer.

Where do we observe Tyndall effect?

We can find Tyndall effect almost everywhere but mostly we find it in the projection of pictures in cinemas due to scattering of light by small particles. This is what we should know in Tyndall effect before knowing more about it.

Tyndall effect

Tyndall effect

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Practise This Question

Garima was reading the newspaper when she suddenly saw the following poster winning the first prize in an event.

The event was most probably organised on: