Wavefronts & Rays (SL IB Physics)

• Waves can travel in both two and three-dimensions:
  • A surface wave propagates in two dimensions and has circular wavefronts (like a circle) such as the surface of water
  • A spherical wave propagates in three dimensions and has spherical wavefronts (like a sphere) such as sound or light

A surface wave has circular wavefronts and moves in two-dimensions propagating outwards from the point source

A three dimensional wave moves with spherical wavefronts in three dimensions like a sphere

• Waves can be represented graphically in two different ways:
  • Wavefronts - lines joining all the points that oscillate in phase and are perpendicular to the direction of motion (and energy transfer)
  • Rays - lines showing the direction of motion (and energy transfer) of the wave perpendicular to the wavefront

Wavefronts and rays for transverse waves travelling in a horizontal plane

• Wavefronts are viewed from above and look like a series of parallel vertical lines
  • Peaks are often represented with a darker line
  • Troughs are represented with a fainter line
  • Some diagrams use only peak wavefronts

Waves can be represented using wavefronts, sometimes diagrams show peak wavefronts and trough wavefronts

• The distance between successive peak wavefronts or (trough wavefronts) is equal to the wavelength of the waves