Which of the following given properties of colloidal particles is its optical property?

Options

A. Brownian movement
B. Colligative properties
C. Electro-osmosis
D. Tyndall effect

Answer

To solve the question regarding the optical property of colloidal particles, we need to analyze the given options:

1. **Brownian Movement**: This is the random motion of colloidal particles due to collisions with molecules of the dispersion medium. It is not an optical property; rather, it is a physical phenomenon related to the kinetic energy of particles.

2. **Colligative Properties**: These properties depend on the number of solute particles in a solution and include boiling point elevation, freezing point depression, and osmotic pressure. They are not optical properties but rather depend on the concentration of particles.

3. **Electroosmosis**: This refers to the movement of liquid through a porous material or gel due to an applied electric field. It is related to the charge on the colloidal particles and is not an optical property.

4. **Tyndall Effect**: This is the scattering of light by colloidal particles, which makes the path of light visible in a colloidal solution. It is indeed an optical property and is dependent on the size of the colloidal particles.

Based on the analysis, the correct answer is:

**Tyndall Effect** (Option 4) is the optical property of colloidal particles.

### Step-by-Step Solution:
1. **Identify the properties listed in the options**.
2. **Analyze each property**:
- Brownian movement: Not an optical property.
- Colligative properties: Not an optical property.
- Electroosmosis: Not an optical property.
- Tyndall effect: An optical property.
3. **Conclude that the Tyndall effect is the only optical property among the options**.