Tyndall effect can be used to distinguish between:

Sugar solution and starch solution

The correct answer is Option (3) → Sugar solution and starch solution

The Tyndall effect refers to the scattering of light by particles in a colloid or very fine suspension. When a beam of light passes through a colloidal solution, the light is scattered by the larger particles, making the path of the light visible. This is particularly useful for distinguishing between different types of mixtures.

Types of Mixtures

True Solutions: In a true solution, the solute (like sugar) dissolves completely at a molecular level in the solvent (water). The solute particles are so small that they do not scatter light. Therefore, solutions like sugar water appear clear and do not exhibit the Tyndall effect.

Colloidal Solutions: A colloid contains larger particles (like starch granules) that do not settle out and can scatter light. These particles are typically in the range of 1 nanometer to 1 micrometer in size. In this case, the light scattered by the particles makes the path of light visible.

Comparing Sugar Solution and Starch Solution

Sugar Solution

Composition: A sugar solution is formed by dissolving sugar (sucrose) in water.

Behavior in Light: The sugar molecules are at the molecular scale, which means they are too small to scatter light. As a result, when a beam of light passes through a sugar solution, it remains clear without any visible scattering. 

Starch Solution

Composition: A starch solution is created by dispersing starch (usually in the form of granules) in water, often requiring heating to fully dissolve.

Behavior in Light: Starch granules are larger than the molecules in a sugar solution. When light passes through a starch solution, the larger starch particles scatter the light, making the path of the beam visible. This scattering indicates that the solution is a colloidal mixture.

Experimental Demonstration

To observe the Tyndall effect, you can perform a simple experiment:

Prepare a Sugar Solution: Dissolve sugar in water and stir until completely dissolved.

Prepare a Starch Solution: Mix starch with water and heat it until the starch is fully dissolved, creating a colloidal solution.

Shine a Light: Use a flashlight or laser pointer to shine a beam of light through both solutions.

Observation: In the starch solution, you will see a visible beam of light due to scattering (the Tyndall effect). In the sugar solution, the light passes straight through without scattering, resulting in a clear appearance.

Conclusion

The Tyndall effect serves as a practical method to differentiate between sugar solutions (true solutions, which are clear) and starch solutions (colloidal solutions, which scatter light). By observing whether light is scattered or passes through without obstruction, you can effectively identify the type of mixture present. This principle is fundamental in colloid chemistry and helps in understanding the behavior of different solutions.