Wavelength is

• A. the distance from trough to trough or from crest to crest of a sound wave
• B. the rate of energy transfer
• C. the speed of a sound wave
• D. the amplitude of a sound wave

Answer: (A)

Wavelength is the spatial distance over which a wave’s shape repeats. In a sound wave, this means the distance from one crest to the next or from one trough to the next. This distance defines how long one cycle of the wave takes as it travels through space. The other properties describe different aspects: the rate at which energy is carried (energy transfer), the speed at which the wave moves through the medium (speed), and the height of the wave peaks (amplitude, related to loudness). Because wavelength specifically measures spatial repetition, it matches the description of crest-to-crest or trough-to-trough distances.