Section Summary

A wave is a disturbance that moves from the point of creation and carries energy but not mass.
Mechanical waves must travel through a medium.
Sound waves, water waves, and earthquake waves are all examples of mechanical waves.
Light is not a mechanical wave since it can travel through a vacuum.
A periodic wave is a wave that repeats for several cycles, whereas a pulse wave has only one crest or a few crests and is associated with a sudden disturbance.
Periodic waves are associated with simple harmonic motion.
A transverse wave has a disturbance perpendicular to its direction of propagation, whereas a longitudinal wave has a disturbance parallel to its direction of propagation.

A wave is a disturbance that moves from the point of creation at a wave velocity v_w.
A wave has a wavelength $λ$ , which is the distance between adjacent identical parts of the wave.
The wave velocity and the wavelength are related to the wave’s frequency and period by $v_{w} = \frac{λ}{T}$ or $v_{w} = f λ .$
The time for one complete wave cycle is the period T.
The number of waves per unit time is the frequency ƒ.
The wave frequency and the period are inversely related to one another.

Superposition is the combination of two waves at the same location.
Constructive interference occurs when two identical waves are superimposed exactly in phase.
Destructive interference occurs when two identical waves are superimposed exactly out of phase.
A standing wave is a wave produced by the superposition of two waves. It varies in amplitude but does not propagate.
The nodes are the points where there is no motion in standing waves.
An antinode is the location of maximum amplitude of a standing wave.
Reflection causes a wave to change direction.
Inversion occurs when a wave reflects from a fixed end.
Refraction causes a wave’s path to bend and occurs when a wave passes from one medium into another medium with a different density.