What is the velocity of a radio wave traveling through free space?
The correct answer is A: Speed of light. The velocity of a radio wave traveling through free space is the speed of light, which is approximately 300,000,000 meters per second (3 × 10^8 m/s) or 186,000 miles per second.
All electromagnetic waves, including radio waves, travel at the speed of light in free space (vacuum). This is a fundamental constant of nature. The speed is the same regardless of frequency or wavelength - all radio waves travel at the same speed. When radio waves travel through other media (like air, water, or coaxial cable), they travel slightly slower, but in free space, they all travel at the speed of light.
Exam Tip
Radio wave speed = Speed of light. Remember: Radio waves travel at the speed of light in free space (approximately 300,000,000 m/s). This is constant for all frequencies.
Memory Aid
"**R**adio **S**peed = **R**apid **S**peed of **L**ight (think 'RS = RSL' = Rapid Speed of Light)"
Real-World Application
You transmit a signal on 2 meters. The radio wave travels from your antenna at the speed of light - 300,000,000 meters per second. Whether you're transmitting on 2 meters, 20 meters, or any other frequency, the wave travels at this same speed. In one second, your signal travels 300,000 kilometers (186,000 miles) through free space.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. The speed of sound is much slower (approximately 343 m/s in air) and applies to sound waves, not radio waves.
Option C: Incorrect. Radio wave velocity is constant (speed of light), not inversely proportional to wavelength. Frequency and wavelength are inversely related, but velocity is constant.
Option D: Incorrect. Radio wave velocity doesn't increase with frequency. All electromagnetic waves travel at the same speed (speed of light) regardless of frequency.
题目解析
The correct answer is A: Speed of light. The velocity of a radio wave traveling through free space is the speed of light, which is approximately 300,000,000 meters per second (3 × 10^8 m/s) or 186,000 miles per second. All electromagnetic waves, including radio waves, travel at the speed of light in free space (vacuum). This is a fundamental constant of nature. The speed is the same regardless of frequency or wavelength - all radio waves travel at the same speed. When radio waves travel through other media (like air, water, or coaxial cable), they travel slightly slower, but in free space, they all travel at the speed of light.
考试技巧
Radio wave speed = Speed of light. Remember: Radio waves travel at the speed of light in free space (approximately 300,000,000 m/s). This is constant for all frequencies.
记忆口诀
**R**adio **S**peed = **R**apid **S**peed of **L**ight (think 'RS = RSL' = Rapid Speed of Light)
实际应用示例
You transmit a signal on 2 meters. The radio wave travels from your antenna at the speed of light - 300,000,000 meters per second. Whether you're transmitting on 2 meters, 20 meters, or any other frequency, the wave travels at this same speed. In one second, your signal travels 300,000 kilometers (186,000 miles) through free space.
错误选项分析
Option B: Incorrect. The speed of sound is much slower (approximately 343 m/s in air) and applies to sound waves, not radio waves. Option C: Incorrect. Radio wave velocity is constant (speed of light), not inversely proportional to wavelength. Frequency and wavelength are inversely related, but velocity is constant. Option D: Incorrect. Radio wave velocity doesn't increase with frequency. All electromagnetic waves travel at the same speed (speed of light) regardless of frequency.
知识点
Radio wave velocity, Speed of light, Free space, Electromagnetic waves
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.