Which of the following statements is correct regarding the propagation of light of different colours of white light in air?

Options

A. Red light moves fastest
B. Blue light moves faster than green light
C. All the colours of the white light move with the same speed
D. Yellow light moves with the mean speed as that of the red and the violet light

Explanation

To determine which statement is correct regarding the propagation of light of different colors of white light in air, we can analyze the properties of light in different mediums. Here is a step-by-step solution:

### Step-by-Step Solution:

1. **Understanding the Medium**:
- Light can travel through different mediums, which can be classified as dispersive or non-dispersive.
- A dispersive medium is one where different colors (or wavelengths) of light travel at different speeds, leading to dispersion. An example of this is a glass prism.

2. **Identifying the Type of Medium**:
- Air is considered a non-dispersive medium. In a non-dispersive medium, all colors of light travel at the same speed.

3. **Analyzing the Statements**:
- **Option 1**: "Red light moves fastest" - This is incorrect in air since all colors travel at the same speed.
- **Option 2**: "Blue light moves faster than green light" - This is also incorrect for the same reason.
- **Option 3**: "All the colors of white light move with the same speed" - This is correct because in air, all colors of light travel at the same speed.
- **Option 4**: "Yellow light moves with the mean speed as that of red light and violet light" - This is misleading as it implies a difference in speeds, which does not occur in air.

4. **Conclusion**:
- The correct statement regarding the propagation of light of different colors of white light in air is **Option 3**: "All the colors of white light move with the same speed."

### Final Answer:
**Option 3**: All the colors of white light move with the same speed.

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