Wave Properties

• Waves can be used to transfer energy and information.
• Transverse waves oscillate perpendicular to the direction of energy transfer of the waves. Ripples on the surface of water are transverse waves. So are all electromagnetic waves.
• Longitudinal waves oscillate parallel to the direction of energy transfer of the waves. Sound waves in air are longitudinal waves.
• Mechanical waves need a medium (a substance) to travel through. They can be transverse or longitudinal waves.
• For any wave, its amplitude is the maximum displacement of a point on the wave from its undisturbed position, such as the height of the wave crest (or the depth of the wave trough) from the position of rest.
• For any wave, its frequency is the number of waves passing a point per second.
• For any wave, its wavelength is the distance from a point on the wave to the equivalent point on the next wave (e.g. from one wave trough to the next wave trough)
• Wave Speed = Frequency x Wavelength
• Plane waves in a ripple tank are reflected from a straight barrier at the same angle to the barrier as the incident waved because their speed and wavelength do not change on reflection.
• Plane waves crossing a boundary between two different materials are refracted unless they cross the boundary at normal incidence.
• Refraction occurs at a boundary between two different materials becasue the speed and wavelength of the waves change at the boundary.
• At a boundary between two different materials, waves can be transmitted or absorbed.
• Sound waves are vibrations that travel through a medium (a substance).
• Sound waves cannot travel through a vacuum.
• To investigate waves, use:

  • A ripple tank for water waves
  • A stretched string for waves in a solid
  • A signal generator and a loudspeaker for sound waves.