Waves

• Wave


  A disturbance which travels through a medium, transferring energy from one point to another without causing any permanent displacement of the medium
• Wave motion


  A process of transferring a disturbance (in form of kinetic energy) from one point to another in a medium without any transfer of particles of the medium
• Wave motion


  • Particles of the medium vibrate or oscillate about their equilibrium positions
  • Wave energy is carried forward and travel over long distances but the medium is limited to only the oscillatory movement of the particles of the medium
• Wave motion


  • Water waves where a leaf on water in a pond simply moves up and down in the same position but it is not carried forward
  • A pulse which moves along a rope towards the fixed end when the loose end is vibrated back and forth
• Mechanical waves


  Waves which require a material medium for them to be propagated
• Mechanical waves


  • Water waves
  • Sound waves
  • Waves on a rope or string
• Electromagnetic waves


  Waves which do not require a material medium for propagation, they can be propagated through a vacuum
• Production and propagation of mechanical waves


  1. Disturbance of any material medium produces mechanical waves

  2. Energy is impacted into the medium and transferred from one particle to another as the particles vibrate about their equilibrium positions
• Mechanical wave production


  • A piece of stone dropped into water
  • A taut rope or string which is pulled (plucked) at a point
• Pulse


  A sudden increase in the magnitude of a physical quantity, shortly followed by a rapid decrease
• Wave front


  A line or surface in the path of an advancing wave on which all the particles are in the same phase or state of disturbance
• Types of Wave fronts

  • Straight lines
  • Concentric circles/arcs
• Plane wave front


  Wave front where the wave travels in one direction
• Spherical or circular wave front


  Wave front where the wave spreads out continuously from the source
• Progressive wave


  A disturbance, transferring energy as it moves away
• Types of progressive waves

  • Transverse waves
  • Longitudinal waves
• Transverse waves


  Waves in which the direction of wave travel is perpendicular to the direction of vibration of the medium
• Examples of Transverse waves


  • Water waves
  • Waves produced in ropes or strings
  • All electromagnetic waves, such as light waves, radio waves etc.
• Longitudinal waves


  Waves in which the direction of wave travel is parallel to the direction of vibration of the medium
• Properties of Longitudinal waves

  • Particles behave as a spring or slinky which is alternately compressed or expanded
  • There are compressed and spaced-out regions called compressions and rarefactions respectively
• Sound waves are longitudinal, meaning they compress and expand the air molecules as they travel.
• The speed of sound is determined by the medium it travels through.
• Reflection: This is when a wave is reflected from a boundary
• Refraction: When a wave changes direction due to change in velocity (speed)
• Diffraction: The bending of waves around an obstacle
• Interference: Occurs when two or more waves meet at the same point
• Transmission: A wave passing through an object without being absorbed
• Interference: When two waves meet at the same point
• Standing waves occur when there is constructive interference between two waves that have been reflected off a barrier
• Destructive interference occurs when two waves meet with equal amplitude but the same phase
• Constructive interference occurs when two waves meet with equal amplitude but opposite phase
• Amplitude: The maximum displacement of a particle from its equilibrium position
• Wavelength: Distance between successive crests/troughs
• Period: The time taken to complete one cycle of a wave
• Frequency: Number of oscillations per second