What is the horizontal distance between crests or troughs of adjacent waves called?

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

Answer: (D)

The horizontal distance between crests or troughs is the wavelength. It measures how far one complete wave cycle extends along the direction the wave moves, basically the spacing between consecutive peaks (or valleys) on the medium. Wavelength links to how the wave carries energy: for a given wave speed, a larger wavelength means fewer crests pass a point per second, and a smaller wavelength means more frequent crests.

Other terms describe different ideas. Frequency is how many waves pass a fixed point each second, not how far apart they are in space. Period is the time it takes for one full cycle to pass a point, the inverse of frequency. Amplitude is the height of the wave from rest, indicating its energy, not the spacing between cycles.