The path of the light remains invisible.
Explanation
The visibility of a light beam passing through a mixture depends on the size of the constituent particles and their ability to scatter light. This phenomenon is known as the Tyndall effect. Mixtures are classified into true solutions, colloids, and suspensions based on particle size.
Detailed Analysis:
- True Solutions: In a true solution, such as copper sulphate dissolved in water, the solute particles are extremely small (less than 1 nm in diameter). Due to this minute size, the particles do not scatter light. Consequently, when a beam of light is passed through a true solution, the path of the light remains invisible.
- Colloids: In contrast, colloidal solutions (e.g., milk or starch solution) have larger particles (between 1 nm and 1000 nm). These particles are large enough to scatter a beam of light, making the path of the light visible. This is the characteristic Tyndall effect.
- Turbidity and Precipitation: Passing light through a solution is a physical observation technique and does not induce chemical changes such as precipitation or turbidity (cloudiness).
Conclusion:
Since copper sulphate in water forms a homogeneous true solution, it does not scatter light. Therefore, the path of the light beam is not visible within the solution.
Key Takeaway:
True solutions do not exhibit the Tyndall effect because their solute particles are too small to scatter light, whereas colloidal solutions do scatter light, rendering the beam's path visible.