Which of the following types of electromagnetic radiation travels at the greatest speed in vacuum ?

Options

A. Radio waves
B. Visible light
C. X rays
D. All of these at the same speed

Answer

To determine which type of electromagnetic radiation travels at the greatest speed in a vacuum, we need to understand a fundamental property of electromagnetic waves.

### Step-by-Step Solution:

1. **Understanding Electromagnetic Waves**: Electromagnetic radiation includes various types of waves such as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

2. **Speed of Electromagnetic Waves in Vacuum**: All electromagnetic waves travel at the same speed in a vacuum. This speed is known as the speed of light, denoted as \( c \), which is approximately \( 3 \times 10^8 \) meters per second.

3. **Comparison of Different Types of Waves**: Since all types of electromagnetic radiation (radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays) travel at the speed of light in a vacuum, there is no difference in speed among them when they are in a vacuum.

4. **Conclusion**: Therefore, the answer to the question is that all types of electromagnetic radiation travel at the same speed in a vacuum. Hence, the correct option is "none of these," indicating that they all travel at the same speed.

### Final Answer:
All types of electromagnetic radiation travel at the same speed in a vacuum, which is the speed of light.

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