Question

Define crest and trough.

Answer 1

To answer this question, you should recall the concept of periodic disturbances. The height and depth of crest and trough determine the amplitude of the wave.

Complete step-by-step answer: A wave is defined as the periodical disturbance which is travelled through the medium from particle to particle and if we observe the movement of the wave then the phase is changed with time. There are characteristic feature of waves like frequency, wavelength, wave number, the velocity of wave etc. Concerning the shape of a wave or periodic disturbance, the most important parts of waves are crest and trough by which it is travelled from one part to another part. The upper region or part is called the crest while the lower part or region is called the trough. The height of each crest is equal to the extent of depth of each trough. The diagrammatic representation can be visualized as follows:

Note: Wavelength of a wave is defined as the distance between two nearest points of the adjacent crest or trough. This is the distance between the wave cycles which are propagated in space. It is a length therefore it is measured in terms of units of length like meters or centimetres or millimetres or Nano-meters or Angstrom units. You should know about constructive and destructive interference. When two waves meet in such a way that their crests line up together, then it’s called constructive interference which results in a wave of higher amplitude. While, in the other case, destructive interference, the crest of one wave meets the trough of another, and the result is a lower total amplitude.