Glossary
Amplitude (a)
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
Example:
A loud sound has a large amplitude, meaning the air particles are displaced significantly from their resting positions.
Compression
A region in a longitudinal wave where the particles of the medium are crowded together, resulting in maximum density and pressure.
Example:
In a sound wave, a compression is the part where air molecules are momentarily pushed close together.
Crest
The highest point or peak of a transverse wave.
Example:
The top of a breaking ocean wave is its crest.
Electromagnetic Wave
A wave that consists of oscillating electric and magnetic fields and does not require a medium to travel, capable of propagating through a vacuum.
Example:
Light from the sun is an electromagnetic wave that travels through the vacuum of space to reach Earth.
Energy
The capacity to do work, which is transferred by a wave without the transfer of matter.
Example:
The energy from a powerful ocean wave can erode coastlines, even though the water itself doesn't travel across the ocean.
Frequency (f)
The number of complete wave cycles that pass a given point per unit of time.
Example:
A high-pitched sound has a high frequency, meaning many sound wave cycles reach your ear per second.
Longitudinal Wave
A wave in which the particles of the medium oscillate parallel to the direction of the wave's propagation.
Example:
When a speaker produces sound, it creates a longitudinal wave by pushing and pulling air molecules back and forth in the same direction the sound travels.
Mechanical Wave
A type of wave that requires a physical medium to transfer energy.
Example:
The vibrations from an earthquake are a mechanical wave that needs the Earth's crust to travel.
Medium
The substance or material through which a mechanical wave propagates.
Example:
Sound waves travel through the medium of air, allowing us to hear.
Period (T)
The time it takes for one complete wave cycle to pass a given point.
Example:
If a pendulum swings back and forth once every 2 seconds, its period is 2 seconds.
Polarization
The direction of oscillation of the electric field vector for an electromagnetic wave, or the direction of vibration for a transverse mechanical wave.
Example:
Sunglasses often use polarization to block horizontally vibrating light waves, reducing glare from reflective surfaces.
Rarefaction
A region in a longitudinal wave where the particles of the medium are spread farthest apart, resulting in minimum density and pressure.
Example:
Following a compression in a sound wave, a rarefaction is the region where air molecules are stretched apart.
Transverse Wave
A wave in which the particles of the medium oscillate perpendicular to the direction of the wave's propagation.
Example:
Shaking a rope up and down creates a transverse wave where the rope segments move vertically while the wave travels horizontally.
Trough
The lowest point or valley of a transverse wave.
Example:
The lowest point between two ocean wave crests is the trough.
Wave
A disturbance that transfers energy through a medium or space 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.
Wave Speed (v)
The rate at which a wave propagates through a medium or space.
Example:
The wave speed of sound in air is approximately 343 m/s, but it's much faster in water.
Wavelength (λ)
The spatial period of a periodic wave, which is the distance over which the wave's shape repeats.
Example:
If you measure the distance from one peak of a water wave to the next consecutive peak, you've found its wavelength.