Electromagnetic waves that are parallel, share a common starting point, have the same frequency and phase, and move through the same medium, form an advancing wavefront at right angles to their direction of travel

  • Sources that emit light in all directions, known as point sources, generate spherical wavefronts.
  • Lasers, which produce a narrow beam of parallel rays, create waves with flat wavefronts.
  • An electromagnetic wave with a flat wavefront is known as a plane wave.
  • In addition to plane waves and spherical waves, there are also cylindrical waves which are produced when a point source is extended along a straight line.
  • The shape of the wavefront can be influenced by interaction with different mediums or obstacles, such as when:
    • Refraction causes the path of light to bend as it crosses the boundary between two transparent media.
    • Dispersion causes light to separate into its constituent wavelengths, each of which bends to a different degree as it crosses the boundary between two transparent media.
    • Diffraction causes light to bend around the edges of obstacles into regions that would otherwise be in shadow.
  • The concept of wavefronts applies not only to light but also to other types of waves such as sound waves or water waves.