What is Wave?

  1. A wave is a disturbance or variation that propagates through a medium, often transferring energy.
  2. Waves travel and transfer energy (its amplitude) and information (its frequency) from one point to another, with little or no permanent displacement of the particles of the medium.
Must Know:
Waves transfer energy without transferring physical matter.

Technical Terms


  1. A phase is the current position in the cycle of something that changes cyclically.
  2. Two vibrating particles are in the same phase if their displacement and direction of motion are the same.
    1. In phase – Same phase
    2. Out of phase – Different phase
    3. Anti-phase – Phase different = 180o


  1. A wavefront is a line or a surface that connects points that are moving at the same phase and has the same distance from the source of the waves.
  2. When a circular wave is formed, a circular wave front is formed.
  3. Characteristics of wavefront:
    1. wavefronts are always perpendicular to the direction of wave propagation. (As shown in the diagram below)
    2. all the points on a wavefront have same distance from the source of the wave.


The wavelength (λ) is defined as the distance between two successive particles which are at the same phase (exactly the same point in their paths and are moving in the same direction.).