Physics

# Section Summary

PhysicsSection Summary

### 13.1Types of Waves

• 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.

### 13.2Wave Properties: Speed, Amplitude, Frequency, and Period

• A wave is a disturbance that moves from the point of creation at a wave velocity vw.
• A wave has a wavelength $λ λ$, 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 $v w = λ T v w = λ T$ or $v w =fλ . v w =fλ .$
• 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.

### 13.3Wave Interaction: Superposition and Interference

• 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.
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