Wavelength

Wavelength L is the horizontal distance between two successive wave crests, the spatial period of the wave. It links to wave period through the dispersion relation L = (gT^2/2 pi) tanh(2 pi h/L), which must be solved iteratively because L appears on both sides. In deep water (depth h greater than L/2) the tanh term approaches one and L = 1.56 T^2 meters; in shallow water (h less than L/20) it reduces to L = T sqrt(gh), so the wave feels the bottom and slows. Wavelength shortens as a wave shoals while its period stays fixed, which steepens the wave toward breaking and governs refraction over varying depth.