### Waves

Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.
Wave
A wave is a mode of energy transfer from one place to another, often with little or no permanent displacement of the particles of the medium, but through oscillations around nearly fixed positions.
Transverse wave
A transverse wave is a wave that causes vibration in the medium in a perpendicular direction to its own motion.
Longitudinal wave
Longitudinal waves are waves that have vibrations along or parallel to their direction of travel.
Frequency
Frequency is the measurement of the number of occurrences of a repeated event per unit of time.
Sound
Sound is a disturbance consisting of vibrations traveling through matter as a longitudinal wave.
Wavelength
Wavelength is the distance between repeating units of a propagating wave of a given frequency.
Electromagnetic radiation, or light, is a self-propagating wave in space with electric and magnetic components.
Standing wave
A standing or stationary wave is a wave that remains in a constant position.
Crest
A crest is the point on a wave with the greatest positive value or upward displacement in a cycle.
Reflection
Reflection is the change in direction of a wave front at an interface between two dissimilar media so that the wave front returns into the medium from which it originated.
Refraction
Refraction is the change in direction of a wave due to a change in its speed when a wave passes from one medium to another.
Interference
Interference is the superposition of two or more waves that results in a new wave pattern.
Acoustics
Acoustics is the branch of physics concerned with the study of sound
Phase
The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0.
Speed of sound
The speed of sound describes how much distance a sound wave travels in a given amount of time.
Decibel
The decibel is a logarithmic unit of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level.
Sound intensity
The sound intensity is defined as the sound power per unit area.
Fundamental frequency
The fundamental tone is the lowest frequency in a harmonic series.
Doppler effect
The Doppler effect is the change in frequency and wavelength of a wave as perceived by an observer moving relative to the source of the waves.
Beat
In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume.
Diffraction
Diffraction refers to various phenomena associated with the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave.
Seismic wave
A seismic wave is a wave that travels through the Earth, most often as the result of a tectonic earthquake, sometimes from an explosion.
Harmonic series
The harmonic seriew refers to the natural frequencies of an oscillator, limited to integer multiples of the lowest possible frequency.
Overtone
An overtone or harmonic is a natural resonance or vibration frequency of a system.
Shock wave
A shock wave is a type of propagating disturbance characterized by an abrupt, nearly discontinuous, change in the characteristics of the medium.
Harmonic
A harmonic or overtone of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency.
Blueshift
Blueshift refers to a shortening of a transmitted signal's wavelength.
Sound pressure
Sound pressure is the pressure deviation from the local ambient pressure caused by an acoustic wave.
Huygens-Fresnel principle
The Huygens-Fresnel principle recognizes that each point of an advancing wave front is the center of a fresh disturbance and the source of a new train of waves.
Capillary wave
A capillary wave or ripple is a wave travelling along the interface between two fluids, whose dynamics are dominated by the effects of surface tension.
Ripple tank
A ripple tank is a shallow glass tank of water used in schools to demonstrate the basic properties of waves. It is a specialized form of a wave tank.
Wavenumber
Wavenumber is a wave property inversely related to wavelength, having SI units of reciprocal meters.
Redshift
Redshift occurs when the electromagnetic radiation emitted from or reflected off an object is shifted toward the red end of the electromagnetic spectrum.
Coherence
Coherence is the property of wave-like states that enables them to exhibit interference. It is also the parameter that quantifies the quality of the interference.
Rayleigh wave
Rayleigh waves are a type of surface wave associated on the Earth with earthquakes and also with ocean waves.
Phase velocity
The phase velocity of a wave is the rate at which the phase of the wave propagates in space.
Group velocity
The group velocity of a wave is the velocity with which the variations in the shape of the wave's amplitude propagate through space.

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