In a longitudinal wave, an arrow pointing to the area between the starting point of one compression and the starting point of another compression indicates what?

In a longitudinal wave, an arrow pointing to the area between the starting point of one compression and the starting point of another compression indicates what?

• A. Crest
• B. Wavelength
• C. Compression
• D. Trough

Answer: (B)

Wavelength is the distance along the direction of travel between identical points in a wave’s pattern. In a longitudinal wave, the pattern consists of compressions (where particles are close together) and rarefactions (where they are spread apart). The arrow pointing from the start of one compression to the start of the next compression marks one full repeat of this pattern, which is the wavelength. Crest and trough are terms for transverse waves, not longitudinal ones, so they don’t describe this spacing. The quantity shown isn’t about how big a compression is (amplitude) or how often the pattern repeats in time (frequency/period), but the spatial length of one complete cycle of the wave.

Wavelength is the distance along the direction of travel between identical points in a wave’s pattern. In a longitudinal wave, the pattern consists of compressions (where particles are close together) and rarefactions (where they are spread apart). The arrow pointing from the start of one compression to the start of the next compression marks one full repeat of this pattern, which is the wavelength. Crest and trough are terms for transverse waves, not longitudinal ones, so they don’t describe this spacing. The quantity shown isn’t about how big a compression is (amplitude) or how often the pattern repeats in time (frequency/period), but the spatial length of one complete cycle of the wave.