Wave Equation v = fλ

Overview

The wave equation v = fλ is always true for any wave in any medium. f is determined by the source, λ is determined by the medium (speed). If the wave moves into a different medium (speed changes), f stays the same but λ changes. In exams: if given wave speed and frequency, find λ = v/f. Or if given λ and v, find f = v/λ.