What is the distance between any two troughs or any two crests on a wave?

• A. Crest
• B. Amplitude
• C. Wavelength
• D. Period

Answer: (C)

The distance between successive crests or successive troughs is the wavelength. This is the spatial length over which the wave repeats its shape, so moving from one crest to the next crest (or from one trough to the next trough) covers one complete cycle in space. In a uniform medium, all such separations are equal, which is why wavelength is the characteristic distance you’d use to describe how far the wave travels before looking the same again. Amplitude describes how tall the wave is, and period is the time for one cycle at a fixed point, not a distance. The crests and troughs themselves are the high and low points, not the distance between them.