On heating a liquid the refractive index generally:

Options

A. Decreases
B. Increase or decrease depending on the rate of heating
C. Do not change
D. Increase

Explanation

To solve the question regarding the effect of heating a liquid on its refractive index, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Refractive Index**: The refractive index (μ) of a medium is a measure of how much light slows down when entering that medium compared to its speed in a vacuum.

2. **Relationship with Temperature**: The refractive index is generally inversely related to temperature. This means that as the temperature of a liquid increases, its refractive index tends to decrease.

3. **Reasoning**: When a liquid is heated, the molecules gain kinetic energy and move more rapidly. This increased molecular motion typically leads to a decrease in density and a corresponding decrease in the refractive index.

4. **Conclusion**: Therefore, upon heating a liquid, the refractive index generally decreases.

5. **Final Answer**: The correct answer is that the refractive index decreases when a liquid is heated.