Wavelength, Frequency, and Speed

Every wave satisfies v = f × λ: speed equals frequency times wavelength. For a fixed speed, higher frequency means shorter wavelength, and vice versa. This single relationship ties together musical pitch, radio channels, and the color of light.

A Tale of Two Speeds

Light in vacuum moves at 299,792,458 m/s — nearly a million times faster than sound in air (343 m/s). That is why a 440 Hz note is a 0.78 m sound wave but a radio signal at the same frequency would have a wavelength of 681 km. The medium sets the scale of everything that follows.

From Wavelength to Photon Energy

For electromagnetic waves, frequency is energy: each photon carries E = h·f, where h is Planck's constant. So wavelength and energy are inversely linked — a blue photon (470 nm) carries more energy than a red one (650 nm), which is why UV light is more damaging than visible light and why X-rays (sub-nanometer) penetrate tissue.