The frequency-wavelength-speed relation governs waves in every medium.

Evidence

One of the most important formulas in this book is f λ = c, where c is the speed of sound, f is the frequency, and λ is the wavelength. This formula applies to waves of any type traveling in all sorts of media, so long as the speed c is taken appropriate to the type of wave and the medium. (The speed c also depends on the wavelength for many waves, but not sound in air or water.) If the frequency f is given, and the wavelength λ measured, the formula fλ = c gives the speed of propagation c of the wave. — Eric J. Heller, Why You Hear What You Hear- An…, 671

Categorization

• DEFINE: Establishes the fundamental wave equation fλ = c that underlies nearly every claim in the book.