One constant ties them together
Every electromagnetic wave — radio, light, X-rays — travels at the same speed in a vacuum. That single fact links its wavelength and its frequency permanently.
Because c is fixed, the two are inverses: stretch the wavelength and the frequency drops in exact proportion. Knowing either one gives the other immediately.
Across the spectrum
| Wave | Wavelength | Frequency |
|---|---|---|
| FM radio | 2.998 m | 100 MHz |
| Green light | 500 nm | 5.996×10¹⁴ Hz |
| X-ray | 0.1 nm | 3×10¹⁸ Hz |
The same equation spans all of it. Green light packs its oscillations more than a million times more tightly than an FM radio wave, which is exactly why one warms your skin and the other passes through walls.
Frequency, energy and why it matters
Frequency is not just a number: through E = h·f it sets how much energy each photon carries. That is the dividing line between harmless and harmful radiation — not how bright it is, but how high its frequency. The converter shows the photon energy alongside the conversion so that jump is visible.
Frequently asked questions
How do you convert wavelength to frequency?
Divide the speed of light by the wavelength: f = c / λ, with c = 299,792,458 m/s in vacuum. Green light at 500 nm gives f = 2.998×10⁸ / 500×10⁻⁹ = 5.996×10¹⁴ Hz, roughly 600 terahertz. To go the other way, λ = c / f.
What is the formula linking them?
c = λf: the speed of light equals wavelength times frequency. Because c is fixed in a vacuum, wavelength and frequency are inversely related — a shorter wave means a higher frequency. The relationship holds for every electromagnetic wave, from radio to gamma rays.
A radio example
An FM station at 100 MHz has a wavelength of λ = c / f = 2.998×10⁸ / 1.0×10⁴ = 2.998 m, about three metres. That is why FM aerials are the length they are, and why radio waves diffract around buildings that visible light cannot.
What is photon energy and why show it?
Each photon carries energy E = h·f, where h is Planck's constant, 6.626×10⁻³⁴ J·s. Higher frequency means more energetic photons, which is why ultraviolet and X-rays can damage tissue while radio waves cannot. The converter shows E so you can compare across the spectrum.
Does this work inside glass or water?
The converter uses the vacuum speed of light. In a medium light slows by the refractive index, so at a fixed frequency the wavelength shortens — about 1.33× shorter in water. For air the difference is tiny and can be ignored; for dense media, divide the speed by the refractive index first.