In which of the following medium the speed of light is maximum ?

Options

A. Water
B. Glass
C. Diamond
D. Vacuum

Explanation

To determine in which medium the speed of light is maximum among air, water, diamond, and vacuum, we can follow these steps:

### Step 1: Understand the Concept of Light Speed
Light travels at different speeds in different mediums. The speed of light is fastest in a vacuum, where there are no particles to slow it down.

### Step 2: Identify the Mediums
The mediums provided in the question are:
- Air
- Water
- Diamond
- Vacuum

### Step 3: Compare the Speed of Light in Each Medium
1. **Vacuum**: In a vacuum, light travels at its maximum speed, approximately \(3 \times 10^8\) meters per second.
2. **Air**: The speed of light in air is slightly less than in a vacuum due to the presence of air molecules.
3. **Water**: The speed of light in water is significantly slower than in air, approximately \(2.25 \times 10^8\) meters per second.
4. **Diamond**: The speed of light in diamond is the slowest among the listed mediums, approximately \(1.24 \times 10^8\) meters per second.

### Step 4: Conclusion
Based on the comparison, the speed of light is maximum in a vacuum.

### Final Answer
The speed of light is maximum in **vacuum**.

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