Wave Motion

Sound is a form of energy produced by a vibrating body, which requires medium to travel. Sound travels in the form of waves. The audible sound has frequency range 20 Hz to 20 kHz.

The sound having frequency less than 20 Hz is called infrasonic sound. The sound having frequency greater than 20,000 Hz are called ultrasonic sound.

Wave: A disturbance created in the medium which propagates in the forward direction with constant velocity without changing its shape, is defined as a wave.

Wave motion: The mode of energy transfer in which a disturbance advances in the forward direction by affecting the medium without mass transfer, is defined as wave motion.

Characteristics of Wave Motion

  1. Wave motion is a disturbance produced in the medium by the repeated periodic motion of the particles of the medium.
  2. Only the wave travels forward whereas the particles of the medium vibrate about their mean positions.
  3. There is a regular phase change between the various particles of the medium. The particle ahead starts vibrating a little later than a particle just preceding it.
  4. The velocity of the wave is different from the velocity with which the particles of the medium are vibrating about their mean positions. The wave travels with a uniform velocity whereas the velocity of the particles is different at different positions. It is maximum at the mean position and zero at the extreme position of the particle.
  5. The medium itself does not move.
  6. The energy and momentum are transferred in the medium.

Whenever disturbance is created in the medium then the particles of the medium start vibrating about their mean positions. The particles of the medium transfer energy or momentum to their neighboring particles and do not move themselves. The particles of the medium are momentarily displaced. The motion of the particles of the medium is simple harmonic motion.

Types of Waves

There are two types of waves, classified according to the vibration of the particles of the medium with respect to the direction of propagation of wave.

  1. Longitudinal waves
  2. Transverse waves