Question T3B04
From subelement T3 - T3B
What is the velocity of a radio wave traveling through free space?
Why is this correct?
Radio waves are electromagnetic waves that travel at the speed of light (approximately 300,000,000 meters per second) through free space. This is a fundamental constant - all electromagnetic waves, regardless of frequency, travel at this same speed in a vacuum. Speed of sound is much slower (about 340 m/s in air), while options C and D incorrectly suggest velocity varies with wavelength or frequency, which it doesn't in free space.
Memory tip
Remember that all electromagnetic radiation - radio waves, visible light, X-rays - shares this same velocity in free space. The frequency and wavelength can change, but their product always equals the speed of light. This relationship (c = f × λ) is fundamental to all RF calculations.
Learn more
This constant velocity enables amateur radio's magic - your 2-meter signal reaches a repeater 50 miles away in less than 0.0003 seconds. In practical terms, this near-instantaneous propagation means the delay you hear in satellite communications comes from processing time, not signal travel time for typical amateur distances. Understanding this helps explain why frequency coordination and emission standards matter for spectrum management.
Think about it
Why do you think all electromagnetic waves travel at the same speed in free space, regardless of whether they're low-frequency HF signals or high-frequency microwave signals?