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📚AP Physics 2 Unit 14 Vocabulary

130 essential vocabulary terms and definitions for Unit 14 – Waves, Sound, and Physical Optics

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📚Unit 14 – Waves, Sound, and Physical Optics
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📚Unit 14 – Waves, Sound, and Physical Optics

14.1 Properties of Wave Pulses and Waves

TermDefinition
amplitudeThe maximum displacement of a wave from its equilibrium position.
compressionA region of high pressure in a longitudinal wave such as a sound wave.
electromagnetic waveA wave consisting of oscillating electric and magnetic fields that are mutually perpendicular and can propagate without requiring a medium.
equilibrium positionThe position of a particle in a wave when it is at rest with no disturbance.
frequencyThe number of complete wave cycles that pass a point per unit time.
longitudinal waveA wave in which particles oscillate parallel to the direction of wave propagation.
mechanical waveA wave that requires a medium to propagate, such as sound or waves on a string.
mediumA material or substance through which a wave travels.
rarefactionA region of low pressure in a longitudinal wave such as a sound wave.
sound waveA mechanical longitudinal wave that propagates through a medium and can be heard.
transverse waveA wave in which the oscillations of the electric and magnetic fields are perpendicular to the direction of propagation.
waveA continuous, periodic disturbance that transfers energy between two locations without transferring matter.
wave pulseA single disturbance that transfers energy without transferring matter between two locations.
wavelengthThe distance between consecutive points of the same phase in a wave, typically denoted by λ.

14.2 Periodic Waves

TermDefinition
amplitudeThe maximum displacement of a wave from its equilibrium position.
equilibriumThe position or state where a wave has zero displacement.
frequencyThe number of complete wave cycles that pass a point per unit time.
periodThe time required for one complete oscillation or cycle of a wave.
periodic waveA wave that repeats its pattern at regular intervals in space and time.
pitchThe perceived quality of a sound that is related to the frequency of the sound wave.
sinusoidal waveA wave whose displacement can be described by a sine or cosine function.
wave speedThe velocity at which a wave propagates through a medium.
wavelengthThe distance between consecutive points of the same phase in a wave, typically denoted by λ.

14.3 Boundary Behavior of Waves and Polarization

TermDefinition
boundaryThe interface between two different media where wave interaction occurs.
frequencyThe number of complete wave cycles that pass a point per unit time.
intensityA measure of the average power transferred by a wave per unit area over one period.
longitudinal waveA wave in which particles oscillate parallel to the direction of wave propagation.
mediumA material or substance through which a wave travels.
polarizationThe process by which charges within a neutral system become separated, with positive charges shifting in one direction and negative charges in another.
powerThe rate at which energy is transferred, converted, or dissipated in an electric circuit, measured in watts.
reflected waveA wave that bounces back from a boundary between two media.
transmitted waveA wave that passes through a boundary and continues traveling into a new medium.
transverse waveA wave in which the oscillations of the electric and magnetic fields are perpendicular to the direction of propagation.
wave inversionA phase reversal of a reflected wave that occurs when the wave travels into a medium where the wave speed decreases.

14.4 Electromagnetic Waves

TermDefinition
blueA visible electromagnetic wave with a wavelength between green and violet.
electric fieldA vector quantity that represents the electric force per unit charge exerted at a given point in space, originating from charged objects.
electromagnetic radiationA collective term for all electromagnetic waves across the entire spectrum.
electromagnetic spectrumThe range of all types of electromagnetic waves ordered by wavelength, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
electromagnetic waveA wave consisting of oscillating electric and magnetic fields that are mutually perpendicular and can propagate without requiring a medium.
gamma raysElectromagnetic waves with the shortest wavelengths in the electromagnetic spectrum, measured in picometers.
greenA visible electromagnetic wave with a wavelength between yellow and blue.
infraredElectromagnetic waves with wavelengths shorter than microwaves but longer than visible light.
magnetic fieldA vector field that exerts a force on moving electric charges, electric currents, and magnetic materials.
microwavesElectromagnetic waves with wavelengths shorter than radio waves but longer than infrared radiation.
orangeA visible electromagnetic wave with a wavelength between red and yellow.
plane waveAn electromagnetic wave characterized by planar wave fronts.
propagationThe process by which electromagnetic waves travel through space without requiring a medium.
radio wavesElectromagnetic waves with the longest wavelengths in the electromagnetic spectrum, measured in kilometers.
redThe visible electromagnetic wave with the longest wavelength in the visible spectrum.
transverse waveA wave in which the oscillations of the electric and magnetic fields are perpendicular to the direction of propagation.
ultravioletElectromagnetic waves with wavelengths shorter than visible light but longer than X-rays.
violetThe visible electromagnetic wave with the shortest wavelength in the visible spectrum.
visible lightElectromagnetic waves with wavelengths that can be detected by the human eye, ranging from red to violet.
wave frontA surface of constant phase in a plane wave, perpendicular to the direction of propagation.
wavelengthThe distance between consecutive points of the same phase in a wave, typically denoted by λ.
X-raysElectromagnetic waves with wavelengths shorter than ultraviolet radiation but longer than gamma rays.
yellowA visible electromagnetic wave with a wavelength between orange and green.

14.5 The Doppler Effect

TermDefinition
Doppler effectThe change in observed frequency of a wave due to relative motion between the source and observer.
observed frequencyThe frequency of a wave as measured by an observer, which may differ from the rest frequency due to relative motion.
relative velocityThe velocity of the wave source with respect to the observer.
rest frequencyThe frequency of a wave emitted by a source at rest relative to the observer.
wave sourceAn object or system that emits waves.

14.6 Wave Interference and Standing Waves

TermDefinition
amplitudeThe maximum displacement of a wave from its equilibrium position.
amplitude variationsPeriodic changes in the amplitude of a resultant wave when two or more traveling wave pulses or waves interact.
antinodeA point on a standing wave where the amplitude is always at maximum.
beat frequencyThe difference between the frequencies of two waves, calculated as |f₁ - f₂|, which determines the rate of amplitude variations.
beatsPeriodic amplitude variations that arise from the addition of two waves with slightly different frequencies.
constructive interferenceThe superposition of waves that results in a wave of greater amplitude, occurring when wavefronts are in phase.
destructive interferenceThe superposition of waves that results in a wave of reduced amplitude, occurring when wavefronts are out of phase.
fundamentalThe standing wave with the longest possible wavelength, also called the first harmonic.
harmonicA standing wave pattern characterized by a specific wavelength, numbered according to its rank from longest to shortest wavelength.
in phaseA condition where two waves have displacements in the same direction at the same location.
interferenceThe phenomenon where the wave nature of light is important and cannot be neglected, involving the superposition of light waves.
nodeA point on a standing wave where the amplitude is always zero.
odd harmonicsHarmonic patterns that can be established in a standing wave with a node at one end and an antinode at the other end.
out of phaseA condition where two waves have displacements in opposite directions at the same location.
second harmonicThe standing wave with the second-longest possible wavelength.
standing waveA wave pattern that results from interference between two waves traveling in opposite directions within a confined region, characterized by fixed points of zero and maximum amplitude.
superpositionThe principle that when two or more waves overlap, the resulting displacement is determined by adding the individual displacements.
third harmonicThe standing wave with the third-longest possible wavelength.
wave interferenceThe interaction of two or more wave pulses or waves that overlap and travel through each other.
wave pulsesIndividual disturbances that travel through a medium, characterized by a single peak or trough.
wavelengthThe distance between consecutive points of the same phase in a wave, typically denoted by λ.

14.7 Diffraction

TermDefinition
central bright fringeThe brightest band at the center of a single-slit diffraction pattern, resulting from constructive interference.
constructive interferenceThe superposition of waves that results in a wave of greater amplitude, occurring when wavefronts are in phase.
destructive interferenceThe superposition of waves that results in a wave of reduced amplitude, occurring when wavefronts are out of phase.
diffractionThe spreading of a wave around the edges of an obstacle or through an opening.
diffraction patternThe pattern of light and dark bands produced when a wave passes through an opening, resulting from interference of multiple wavefronts.
interference patternThe observable pattern created by the superposition of multiple waves, resulting in regions of constructive and destructive interference.
monochromatic lightLight of a single wavelength or frequency.
path length differenceThe difference in distances traveled by two wavefronts, denoted as ΔD, which determines the type of interference between them.
single-slit diffractionThe diffraction pattern produced when a wave passes through a single narrow opening.
small angle approximationA mathematical approximation used when the angle θ is less than 10°, allowing simplified relationships between diffraction parameters.
wavefrontA surface of constant phase in a propagating wave, perpendicular to the direction of wave propagation.
wavelengthThe distance between consecutive points of the same phase in a wave, typically denoted by λ.

14.8 Double-Slit Interference and Diffraction Gratings

TermDefinition
center maximumThe central bright fringe in a diffraction pattern, where all wavelengths of white light interfere constructively and appear white.
central bright fringeThe brightest band at the center of a single-slit diffraction pattern, resulting from constructive interference.
constructive interferenceThe superposition of waves that results in a wave of greater amplitude, occurring when wavefronts are in phase.
destructive interferenceThe superposition of waves that results in a wave of reduced amplitude, occurring when wavefronts are out of phase.
diffraction gratingAn optical device consisting of many evenly spaced parallel slits or openings that produce an interference pattern by superimposing numerous diffraction patterns.
diffraction patternThe pattern of light and dark bands produced when a wave passes through an opening, resulting from interference of multiple wavefronts.
dispersionThe separation of white light into its component wavelengths or colors based on their different angles of diffraction.
higher-order maximaBright fringes in a diffraction pattern at positions beyond the central maximum, corresponding to m = 1, 2, 3, and so on.
monochromatic lightLight of a single wavelength or frequency.
order of maximum brightnessThe integer m that designates the position of bright fringes in an interference pattern, where m = 0 for the central maximum, m = 1 for the first-order maximum, and so on.
path length differenceThe difference in distances traveled by two wavefronts, denoted as ΔD, which determines the type of interference between them.
slit separationThe distance between two adjacent slits, represented by the symbol d.
small angle approximationA mathematical approximation used when the angle θ is less than 10°, allowing simplified relationships between diffraction parameters.
wave diffractionThe bending and spreading of a wave as it passes through an opening or around an obstacle.
wave interferenceThe interaction of two or more wave pulses or waves that overlap and travel through each other.
wavefrontA surface of constant phase in a propagating wave, perpendicular to the direction of wave propagation.
wavelengthThe distance between consecutive points of the same phase in a wave, typically denoted by λ.
white lightLight composed of all visible wavelengths combined, appearing colorless.
Young's double-slit experimentAn experiment demonstrating wave properties of particles through the observation of interference patterns.

14.9 Thin Film Interference

TermDefinition
absorbedLight that is taken in by a medium and converted to other forms of energy rather than being reflected or transmitted.
antireflection coatingA thin layer applied to a surface that uses destructive interference to eliminate reflected light by controlling thickness and index of refraction.
constructive interferenceThe superposition of waves that results in a wave of greater amplitude, occurring when wavefronts are in phase.
destructive interferenceThe superposition of waves that results in a wave of reduced amplitude, occurring when wavefronts are out of phase.
index of refractionA measure of how much a medium slows down light compared to its speed in vacuum, determining the degree of bending and reflection of light at interfaces.
normal incidenceLight striking a surface at a perpendicular angle (90 degrees) to the surface.
oil filmsA practical example of thin-film interference where spectrum colors are observed due to variations in film thickness.
phase changeA shift in the phase of a light wave upon reflection, which can be 180 degrees or zero degrees depending on the relative indices of refraction of the materials.
reflected rayA ray of light that bounces off a surface after reflection.
refractedThe bending of light as it passes from one medium to another with a different index of refraction.
soap bubblesA practical example of thin-film interference where color variations result from differences in film thickness.
thin filmA medium whose thickness is comparable to the wavelength of light, causing interference effects when light interacts with it.
thin-film interferenceThe wave interference pattern that occurs when light reflects from the two surfaces of a thin film, resulting in constructive or destructive interference.
transmittedLight that passes through a medium rather than being reflected or absorbed.
wave interferenceThe interaction of two or more wave pulses or waves that overlap and travel through each other.
wavelengthThe distance between consecutive points of the same phase in a wave, typically denoted by λ.