Tyndall Effect – In colloidal dispersion, the Tyndall Phenomenon is a light scattering phenomenon that shows no light in a real solution. This phenomenon has been used to determine if a mixture contains a tangible solution or a colloid. The Tyndall effect is seen when sunlight passes through a dense forest canopy. Let us have a better understanding of the Tyndall effect in class 10.
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WHAT IS THE TYNDALL EFFECT?
The Tyndall effect is one of the important topics in class 10. The Tyndall effect is the dispersion of light as a light beam passes through a colloid. When light beams are focused on particles in a colloid, the Tyndall effect occurs. This effect can be detected in all colloidal fluids, even the tiniest suspensions. As a result, this phenomenon may tell if a solution is a colloid or not.
The intensity of dispersed light depends on the density and frequency of the suspended particles. The more the contact between the particles and the light beam, the greater the light scattering and the greater the chance of observing a Tyndall effect.
The Tyndall effect scatters blue light more than red light, similar to Rayleigh scattering. This is because red light has a longer wavelength than blue light. Therefore, the smoke emitted by motorcycles might appear blue at times. When a light beam passes through a colloid, colloidal particles in the solution hinder the beam from going completely through.
John Tyndall, an Irish physicist, was the first to discover the Tyndall effect.
The particles that create the Tyndall effect can have sizes ranging from 40 to 900 nanometers (1 nanometer equals 10-9 meters). The wavelength of visible light extends from 400 to 750 nanometers.
EXPLANATION OF TYNDALL EFFECT WITH THE HELP OF EXAMPLE
Let’s try to understand the Tyndall effect by considering the difference between a colloidal solution that exhibits the Tyndall effect and a real solution that does not. As we all know, milk is an example of a colloidal solution and the class of colloids is an emulsion in which milk fat particles are disseminated in water. Unlike a genuine solution, such as sugar dissolved in water, the constituent particles of milk are larger but small enough to fall within the visible light spectrum. Milk has a higher optical density than a sugar-water solution.
Milk fat particles cannot be separated by filtration but can be separated by centrifugation, but sugar solution can neither be separated by filtration nor by centrifugation. If you are given both the solutions, it would be quite difficult to tell whether the milk or sugar solution is a genuine solution or a colloidal solution simply by looking at them. The Tyndall effect can be employed to distinguish between the two types of solutions in this case.
When a light beam passes through a sugar solution in a clear beaker or glass container, the path of the light beam is invisible. When the same beam of light is blazed against milk in a transparent glass or beaker, the course of the light beam and the milk inside the beaker/glass can readily be tracked.
Thus, the Tyndall effect can be used to easily distinguish between the two liquids based on their constituent particles, such as separating milk, which is a colloidal solution, from a real solution, such as sugar.
EXAMPLES OF THE TYNDALL EFFECT FOR CLASS 10
Other examples of the Tyndall effect are:
When a torch is turned on in a foggy environment, the path of light becomes visible. Water droplets in the fog produce light scattering in this situation.
When numerous dust particles are suspended in the air, such as when light travels through a dense forest canopy, the path of the sun becomes visible.
Opaque glass has a bluish tint when viewed from the side. However, when light shines through the glass, it produces orange-colored light.
THE TYNDALL EFFECT AS A FACTOR RESPONSIBLE FOR BLUE EYE COLOUR
The fundamental difference between blue, brown, and black irises is the amount of melanin in one of the layers of the iris. When compared to a black iris, the layer of a blue iris contains a smaller quantity of melanin, making it translucent. The Tyndall effect scatters light when it is incident on this translucent layer.
When compared to red light, blue light has a shorter wavelength and is hence scattered more. A layer deeper in the iris absorbs unscattered light. Because most of the scattered light is blue, these irises take on a distinctive blue tinge.
Light scattering is engaged in a variety of processes. Two examples are Mie scattering and Rayleigh scattering. The light is scattered by air particles, resulting in a blue sky. This is an example of Rayleigh scattering.
However, when the sky is overcast, light scattering is induced by the relatively large cloud droplets, which is an example of Mie scattering.
When light passes through colloidal liquids, it causes this phenomenon. The Tyndall effect is used in commercial and laboratory applications to determine the particle size of aerosols due to light scattering.