In physics and mathematics, waves are disturbances (changes from an equilibrium) of one or more fields such that the field values oscillate repeatedly about a stable equilibrium (resting) value.


Animation of two waves, the green wave moves to the right while blue wave moves to the left, the net red wave amplitude at each point is the sum of the amplitudes of the individual waves. Note that f(x,t) + g(x,t) = u(x,t). image: wikipedia

If the relative amplitude of oscillations at different points in the field remains constant, the waves are said to be standing waves. If the relative amplitude at different points in the field changes, the waves are said to be traveling waves.

Waves can only exist in fields when there is a force that tends to restore the field to equilibrium.

What types of waves are studied?

The types of waves most commonly studied in physics are mechanical and electromagnetic. 

For mechanical waves, stress and strain fields oscillate about a mechanical equilibrium. A traveling mechanical wave is a local deformation (strain) in some physical medium that propagates from particle to particle by creating local stresses that cause strain in neighboring particles too. 

  • For example, sound waves in air are variations of the local pressure that propagate by collisions between gas molecules. 

  • Other examples of mechanical waves are seismic waves, gravity waves (note this is different to gravitational waves), vortices, and shock waves. 

For electromagnetic waves the electric and magnetic fields oscillate. A traveling electromagnetic wave (light) consists of a combination of variable electric and magnetic fields, that propagates through space according to Maxwell's equations. Electromagnetic waves can travel through transparent dielectric media or through a vacuum; examples include radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

Source adapted from: Wikipedia contributors. (2019, October 30). Wave. In Wikipedia, The Free Encyclopedia. Retrieved 08:30, November 3, 2019, from https://en.wikipedia.org/w/index.php?title=Wave&oldid=923777443