The wave equation fλ equals c applies to any wave in any medium

Evidence

From Figure 1.5, we can see that both the quasi-longitudinal and transverse shear waves in bars and plates are nondispersive. That is, their phase velocity is independent of frequency. This means that they also have a frequency-independent group velocity and therefore preserve the waveshape of a sound wave containing many frequency components. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 132 (#qualifies, via linked claim)

Categorization

• XREF: connects to: Frequency, wavelength, and velocity determine one another; Longitudinal and shear waves preserve waveshape because phase velocity is frequency-independent — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 132; Dispersive media split wave speed into phase and group velocity (+1 more)

Related

• Longitudinal and shear waves preserve waveshape because phase velocity is frequency-independent (similarity 0.94)
• Bending waves disperse with frequency, so their waveshape is not preserved (similarity 0.88)
• Dispersive media split wave speed into phase and group velocity (similarity 0.85)
• The frequency-wavelength-speed relation governs waves in every medium. (similarity 0.83)
• Materials with movable boundaries support wave types beyond longitudinal waves. (similarity 0.83)
• Dispersion causes bending waves to lose their original waveshape (similarity 0.82)
• Bending wave speed grows as the square root of frequency (similarity 0.82)
• Frequency stays constant across media, so slow speed shortens wavelength (similarity 0.82)
• Shear waves stay non-dispersive while bending waves disperse with frequency (similarity 0.81)
• Bending waves disperse because their wavenumber grows only with the square root of frequency (similarity 0.81)
• Phase velocity measures single-frequency speed while group velocity tracks the signal envelope (similarity 0.80)
• Wave speed, frequency, and wavelength are linked by fλ = c (similarity 0.80)
• Waves always refract toward regions of slower wave speed (similarity 0.79)
• Phase velocity and group velocity differ in dispersive media (similarity 0.79)
• Fast wave propagation does not require fast motion of the medium itself. (similarity 0.78)

Broader Connections

• Frequency, wavelength, and velocity determine one another #expands (0.90)
• Longitudinal and shear waves preserve waveshape because phase velocity is frequency-independent #qualifies (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 132
• Dispersive media split wave speed into phase and group velocity #qualifies (0.75)