Glossary
Amplitude
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
Example:
Turning up the volume on your speaker increases the amplitude of the sound waves, making them louder.
Compression
A region in a longitudinal wave where the particles of the medium are crowded together, resulting in higher density and pressure.
Example:
When a speaker pushes air outwards, it creates a compression of air molecules that travels as a sound wave.
Crest
The point on a transverse wave where the displacement of the medium is at its maximum positive value.
Example:
Surfers ride the crest of a wave, which is its highest point.
Cycle
One complete oscillation or vibration of a wave, from one point on the wave to the next identical point.
Example:
From the moment a pendulum swings from its highest point on one side, through its lowest, and back to its highest point on the same side, it has completed one cycle.
Equilibrium Position
The resting or undisturbed position of the particles in a medium before a wave passes through.
Example:
When a string is perfectly still and flat, every point on it is at its equilibrium position.
Frequency
The number of complete cycles or oscillations of a wave that occur in a given amount of time.
Example:
A guitar string vibrating 440 times per second has a frequency of 440 Hz, producing the musical note A4.
Longitudinal Wave
A wave in which the particles of the medium oscillate parallel to the direction of the wave's propagation.
Example:
Sound traveling through air is a longitudinal wave, as air molecules vibrate back and forth in the same direction the sound is moving.
Mechanical Wave
A type of wave that requires a physical medium to propagate and cannot travel through a vacuum.
Example:
Ocean waves are a classic example of a mechanical wave, needing water to travel and transfer energy.
Medium
The material or substance through which a mechanical wave travels.
Example:
For a sound wave, the air, water, or solid material it passes through acts as its medium.
Period
The time it takes for one complete cycle or oscillation of a wave to occur.
Example:
If a pendulum swings back and forth once every 2 seconds, its period is 2 seconds.
Rarefaction
A region in a longitudinal wave where the particles of the medium are spread apart, resulting in lower density and pressure.
Example:
Following a compression, a rarefaction occurs where the air molecules are stretched out, creating a region of lower pressure.
Transverse Wave
A wave in which the particles of the medium oscillate perpendicular to the direction of the wave's propagation.
Example:
Imagine shaking a rope up and down to send a pulse along it; this creates a transverse wave where the rope moves vertically while the wave travels horizontally.
Trough
The point on a transverse wave where the displacement of the medium is at its maximum negative value.
Example:
The lowest point between two waves in the ocean is called the trough.
Velocity of a Wave
The speed at which a wave propagates through a medium, determined by the product of its wavelength and frequency.
Example:
The velocity of a wave on a stretched string depends on the string's tension and mass density, not how hard you pluck it.
Wave
A traveling disturbance that transfers energy and momentum without transferring matter.
Example:
When you drop a pebble into a pond, the ripples that spread outwards are a wave transferring energy across the water's surface.
Wavelength
The spatial period of a wave, which is the distance over which the wave's shape repeats.
Example:
If you measure the distance from the peak of one ocean wave to the peak of the next, you've found its wavelength.