Tyndall Effect

The Tyndall effect is the light scattering by a colloid or extremely tiny solution of particles. Tyndall scattering, also known as that phenomenon, is similar to Rayleigh scattering in that the intensity of the scattered light is inversely related to the wavelength’s fourth power, with blue light being scattered far more intensely than red light. The blue colour that sometimes appears in the smoke from motorbikes, especially two-stroke bikes, where particles made of burned engine oil are responsible for this colour, serves as an example in daily life. 

On the other hand, the Tyndall effect is caused by particles of the same size as the wavelength of light, whereas Rayleigh scattering is caused by particles much smaller than the wavelength of light. The British physicist John Tyndall, who conducted the effect’s initial and in-depth studies, is honored with this effect’s name.

What is Tyndall Effect?

The scattering of light (light beam) through a colloidal solution is referred to as the Tyndall effect. When particles in a colloid scatter light beams directed at them, this is known as the Tyndall effect. This effect can be seen in all colloidal solutions and some very fine suspensions. 

For example, the Tyndall effect is exhibited by starch solution as it is a colloidal solution. Thus, it can be said that the Tyndall effect is observed in a colloidal solution. 

Tyndall Effect in Colloidal Solution

Tyndall effect is the phenomenon of scattering of a beam of light by the particles in a colloid. Here is the Tyndall effect diagram showing how and why this phenomenon occurs:

As shown in the above figure, When a strong, convergent light beam passes through a colloidal solution, its path is visible when the light beam is viewed perpendicularly. Such a phenomenon is called the Tyndall effect and so we say that Tyndall effect is due to the scattering of light by the colloidal particles. In the Tyndall effect, the colloidally suspended particles outline the path of a strong beam of light because of the scattering of light by the colloidal particles.

As a result, it can be used to determine whether a given solution is a colloid. The intensity of scattered light is affected by the density of colloidal particles and the frequency of incident light.

When a light beam passes through a colloid, the colloidal particles in the solution prevent the beam from completely passing through. Light is scattered when it collides with colloidal particles (it deviates from its typical trajectory, which is a straight line). This scattering reveals the path of the light beam, as shown below. 

Tyndall Effect	Solution	Colloid	Suspension
	Do not scatter light	Scatter light (Tyndall effect)	May either scatter light or be opaque

The Irish physicist John Tyndall discovered (and is named after) the Tyndall effect. The particles that cause the Tyndall effect can have diameters ranging from 40 to 900 nanometers (1 nm = 10^-9 m). In comparison, the visible light spectrum has wavelengths ranging from 400 to 750 nanometers.

Tyndall Effect Example

• The Tyndall effect can be demonstrated by shining a flashlight beam into a glass of milk. You might want to use skim milk or dilute the milk with a little water to see how the colloid particles affect the light beam.
• The blue color of smoke from motorcycles or two-stroke engines is an example of how the Tyndall effect scatters blue light.
• The Tyndall effect is responsible for the visible beam of headlights in fog. The light is scattered by the water droplets, making the headlight beams visible.
• In commercial and laboratory settings, the Tyndall effect is used to determine the particle size of aerosols.
• The Tyndall effect is visible in opalescent glass. Although the glass appears blue, the light shining through it appears orange.
• The blue eye color is caused by Tyndall scattering through the translucent layer over the iris of the eye.

How does the Tyndall Effect influence the Colour of Blue Eyes?

The quantity of melanin in one of the layers of the iris is the main difference between blue, brown, and black coloured irises. When compared to a black iris, the layer in a blue iris contains significantly less melanin, which makes it translucent. The Tyndall effect causes light to be scattered as it strikes this translucent layer.

Blue light is more widely diffused than red light because it has a shorter wavelength. The light that is not scattered is absorbed by a deeper layer in the iris. These irises get their characteristic blue colour because the bulk of the dispersed light is blue.

FAQs on Tyndall Effect

Question 1: Define Tyndall Effect.

Answer:

The scattering of light (light beam) through a colloidal solution is referred to as the Tyndall effect. When particles in a colloid scatter light beams directed at them, this is known as the Tyndall effect. 

Question 2: Which of the following will show the Tyndall Effect:

• Milk 
• Salt Solution
• Starch Solution 
• CuSO₄ Solution

Answer:

Tyndall effect is shown by Milk and Starch Solution, out of the four given solutions. This is because milk and starch solutions are colloidal solutions. Since milk is a colloidal solution of fat and protein. 

Question 3: Does the Starch solution show the Tyndall effect?

Answer:

The starch solution exhibits a very weak or almost no Tyndall effect because starch is a lyophilic sol and starch solution have very tiny and solvated particles. 

Question 4: Who discovered the Tyndall effect?

Answer:

The Irish physicist John Tyndall discovered (and is named after) the Tyndall effect.

Question 5: Does Suspension show the Tyndall effect?

Answer:

Suspension is the heterogeneous mixtures having particle size > 1000 nm, and scatter in the path of the incident light. These p[articles may settle down later or sooner, then helps to follow the Tyndall effect. Hence, suspension show the tyndall effect. 

Question 6: Will Copper Sulphate Solution show the Tyndall effect?

Answer:

The copper Sulphate Solution does not show Tyndall effect. Because they have particle size less than 1 nm in diameter, which are even not visible to the naked eye.

Question 7: Does Face cream show the Tyndall effect?

Answer:

Yes, face cream shows the Tyndall effect. 

Question 8: What are the properties of colloids?

Answer: 

The properties of a colloid are as follows:

• A colloid is a mixed substance that is heterogeneous in nature.
• A colloid’s particles are too small to be seen individually with the naked eye.
• Colloids are large enough to scatter a light beam passing through them and reveal their path.
• They do not settle down when left alone, indicating that a colloid is quite stable.

Question 9: What is a Tyndall cone?

Answer: 

When light passes through a colloidal solution, the path of light appears to be a bright cone due to Tyndall scattering. This is due to the fact that colloidal particles scatter light in all directions. Tyndall cone is the name given to this.