Traveling EM Waves
E and B fields propagating at c. Builds on Maxwell's Equations.
A radio station broadcasts at 100 MHz. A gamma-ray telescope detects rays at 10²¹ Hz. Both signals are electromagnetic waves traveling through the vacuum of space.
Which wave travels faster through empty space?
They travel at EXACTLY the same speed — the speed of light, c = 299,792,458 m/s! Radio waves, microwaves, visible light, X-rays, gamma rays — every electromagnetic wave in vacuum moves at c. What differs is their frequency and wavelength, not their speed.
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Watch the E and B fields oscillate perpendicular to each other and to the direction of travel. All EM waves share this structure — only the wavelength changes.
c = λf = 1/√(ε₀μ₀)
The speed of light emerges from the electric and magnetic properties of empty space. Higher frequency just means shorter wavelength — the speed never changes in vacuum.
Radio waves (wavelengths of meters) carry music, data, and Wi-Fi. Same physics as visible light, just 10 million times longer wavelength.
The Sun’s visible light takes 8 minutes 20 seconds to reach Earth, traveling 150 million km at exactly c.
The oldest light in the universe, emitted 380,000 years after the Big Bang, has been traveling at c for 13.8 billion years and is now stretched to microwave wavelengths.
MRI uses radio-frequency EM waves to flip hydrogen nuclei in your body, creating detailed images without ionizing radiation.
“Electric fields make magnetic fields, magnetic fields make electric fields, and together they race through space at c — the speed limit of the universe.”
EM Wave Lab
Explore the full electromagnetic spectrum. Adjust frequency and wavelength and watch E and B fields propagate together. See where your wave sits on the spectrum — from radio to gamma rays.
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Start with a visible-light frequency (~5 × 10¹⁴ Hz). Now slide to radio frequencies and watch the wavelength stretch to meters. Slide to X-ray frequencies and watch it shrink to nanometers. Notice: the wave always moves at the same speed!
All electromagnetic waves are the same phenomenon — oscillating E and B fields. What we call ‘radio,’ ‘light,’ or ‘gamma rays’ is just a matter of frequency. The speed is always c.