Which describes the wavelength of a wave?

a.
the distance from the crest to the rest position

b.
the distance from one point on a wave to the next similar point

c.
the distance from the crest to the trough

d.
the distance from the rest position to the trough

So we want to know what physical quantity represents the wavelength of a wave. Waves have a few phyiscal quantities that are used to describe them. Frequency, amplitude and wavelength. Frequency is the number of oscillations in a specific time interval, amplitude is the maximal elongation of a wave and wavelength is the distance from one point ona a wave to the next similar point. So the correct answer is B.