Question

S-I: Scattering of light by dispersed particles of colloidal system is known as Tyndall effect.
S-II: The diameter of the dispersed particles should not be much smaller than the wavelength of the light used.

• A. Both S-I and S-II are correct
• B. S-I is correct but S-II is incorrect
• C. Both S-I and S-II are incorrect
• D. S-I is incorrect but S-II is correct

Hint:

Tyndall Effect Requirements:

• Colloidal size range: \(1 \text nm - 1000 \text nm\)
• Dispersed particles must be large enough to scatter light.
• The medium should be transparent and should allow scattering to be visible.

Answer 1

The Correct Option is A

The Tyndall effect is an important property of colloidal systems. It is defined as the scattering of visible light by particles in a colloid or in very fine suspensions.

• Statement S-I: Correct. When a beam of light passes through a colloid, the light gets scattered by the dispersed particles in the colloidal solution, and this scattered light becomes visible. This is known as the Tyndall effect. Examples: sunlight scattering through mist, smoke in a dark room, etc.
• Statement S-II: Also correct. For the Tyndall effect to be observable, the particle size of the dispersed phase should be comparable to the wavelength of visible light (around 400–700 nm). If the particle size is much smaller, no significant scattering occurs, and thus, no Tyndall effect will be seen.

Both conditions are essential and valid.

Answer 2

Step 1: Understanding Statement I (S-I)
The scattering of light by dispersed particles in a colloidal system is called the Tyndall effect. When a beam of light passes through a colloidal solution, the particles scatter the light, making the path of the light visible. This effect helps distinguish between a true solution and a colloidal solution.

Step 2: Understanding Statement II (S-II)
For the Tyndall effect to be observable, the diameter of the dispersed colloidal particles must be comparable to or larger than the wavelength of the incident light. If the particles are much smaller than the wavelength of light, the scattering will be negligible and the effect won't be seen clearly.

Step 3: Relationship between particle size and wavelength
Visible light has wavelengths roughly between 400 nm to 700 nm. Colloidal particles generally range from 1 nm to 1000 nm, so when particle sizes are within this range, scattering occurs significantly.

Step 4: Conclusion
Both statements S-I and S-II are correct because the Tyndall effect is indeed the scattering of light by colloidal particles, and for this scattering to be noticeable, the particle size must be not much smaller than the wavelength of light.