Assertion : Aqueous gold colloidal sol is red in colour.
Reason : The colour arised due to scattering of light by particles of gold.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, mark (1)
B. If both Assertion & Reason are true but reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Resson are false statements , then mark (4)

Answer

To solve the question regarding the assertion and reason about the color of aqueous gold colloidal sol, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
**Assertion**: Aqueous gold colloidal sol is red in color.

- **Explanation**: Gold colloidal solutions exhibit different colors depending on the size of the gold particles. When the particles are very small (in the nanometer range), the solution appears red. This phenomenon occurs due to the interaction of light with the colloidal particles.

**Conclusion**: The assertion is true.

### Step 2: Analyze the Reason
**Reason**: The color arises due to scattering of light by particles of gold.

- **Explanation**: The color observed in colloidal solutions is indeed due to the scattering of light, a phenomenon known as the Tyndall effect. When light passes through the colloidal solution, the particles scatter the light, and the color we see is a result of this scattering. The specific color depends on the size of the particles and the wavelength of light that is scattered.

**Conclusion**: The reason is also true.

### Step 3: Relationship Between Assertion and Reason
- The reason provided explains why the assertion is true. The red color of the aqueous gold colloidal sol is due to the scattering of light by the gold particles, which aligns perfectly with the assertion.

### Final Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

### Answer
The correct option is: Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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