What is defined as the horizontal distance between two adjacent crests of a wave?

The horizontal distance between two adjacent crests of a wave is referred to as the wavelength. In wave mechanics, the wavelength is a key concept that provides insights into the behavior and characteristics of waves. It is measured from one crest (the highest point of the wave) to the next crest, indicating how spread out the wave is in space.

Wavelength is crucial for understanding various properties of waves, such as their energy and how they interact with matter. For example, in the electromagnetic spectrum, different wavelengths correspond to different types of radiation, influencing how they are absorbed, transmitted, or reflected by materials.

In contrast, frequency relates to how many waves pass a point in a given time period, rather than the distance between them, and the terms crest and trough refer specifically to the peaks and valleys of a wave, rather than the spacing between them. Thus, identifying the distance between crests accurately defines what wavelength represents.