What is wavelength?

• A. The distance from one point of a sound wave to the same point on the next wave.
• B. Velocity divided by frequency
• C. Feet per cycle
• D. Amplitude of the wave

Answer: (A)

Wavelength is the distance between identical points on successive waves, such as crest to crest or trough to trough. This directly measures the spatial period of the wave as it propagates through a medium. For a sound wave, the spacing between successive crests in the air is the wavelength, showing how long one complete wave pattern extends in space. While you can also express wavelength with the formula λ = v / f (speed divided by frequency), that is a derived relationship you use when you know the wave’s speed and frequency. The other ideas—amplitude being the height of the wave, or feet per cycle mixing a length with a time concept—do not describe the spatial repetition the way wavelength does. So the distance from a point on one wave to the same point on the next wave best captures what wavelength is.