This interactive glossary will not only define terms used throughout the lab but also show graphics or video that illustrate the term.
Anti-Nodes: A region of a standing wave or interference pattern where the waves constructively interfere causing large positive and negative oscillations. Click for a graphic and/or compare to the movie.
Compression: In a compressional (logitudinal) wave, it's the part of the wave that is squeezed together. Click here to see a compression (picture). Back to Top Back to Wave Index
Compressional: A type of wave where the disturbance is created in the same plane as the direction of wave motion (propagation). Click here to see a compressional wave movie. Back to Top Back to Wave Index
Crest: In a transverse wave, this is the part of the wave that rises "above" (positive) the rest state of the medium. Click here to see a crest graphic. Back to Top Back to Wave Index
Diffraction: A situation where
waves curve or spread-out as they pass through an opening or move around
a barrier. Click here to see water waves diffracting (movie).
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to Wave Index
Frequency: The rate at which waves are produced by a source. The frequency of produced waves does not change regardless or medium unless the source itself changes. In a particular medium, changes in wave frequency cause inverse changes in wavelength. For example an increase in frequency will cause the resulting waves to have a smaller wavelength. Click here to see the effects increasing the frequency of waves (movie) Back to Top Back to Wave Index
Interference: The overlapping or collision of two or more waves. Waves move through each other, but while they overlap they can make a larger disturbance if their amplitudes are the same (constructive interference) or will make a smaller disturbance if their amplitudes (destructive interference). Click to see a constructive interference movie. Click to see a destructive interference movie. Back to Top Back to Wave Index
Interference Pattern: A series of repeating nodes and anti-nodes that form when two or more waves contiunously overlap. This happens for many reasons, a few of which are: waves passing through two small openings, placing two identical sources near each other, and creating standing waves. Click for a 2-D wave pattern graphic. Back to Top Back to Wave Index
Law of Reflection: Rule for determining how a wave will reflect. It states that that the reflected angle of wave motion should equal the incident angle of wave motion. These angles are mesured by comparing the direction of wave motion to an imaginary line drwan perpendiclarly (normal) to the reflecting suface. Click to see a graphic description of these angles. Back to Top Back to Wave Index
Medium: The material through which a physical or mechanical wave travels. The medium is the sole factor that determines the velocity that a wave has while in that medium. Light waves do not require a medium. This movie shows that the wave moves through the medium. Back to Top Back to Wave Index
Nodes: A region of a standing wave or interference pattern where the waves are always destructively interfering with each other. Click for a graphic and/or compare to the movie. Back to Top Back to Wave Index
Propagation: The direction of motion of a wave though a medium. One dimensional (for example a slinky) waves propagate in a straight line. Two dimensional waves may propagate in a straight line (plane waves) or in all directions on a surface (circular waves on a pond/ ripple/tank). Three dimensional waves can propagate in all directions (like a light bulb illuminating a room). Back to Top Back to Wave Index
Pulse: A single disturbance made in a medium. This is not a full wave because it consists of a half-vibration: either a single crest or compression but no trough or rarefaction. Click for a graphic. Back to Top Back to Wave Index
Rarefaction: In a compressional (logitudinal) wave, it's the part of the wave that is "stretched out". Click here to see a rarefaction picture. Back to Top Back to Wave Index
Reflection: A phenomenon that occurs when waves strike barriers or other media. In the case of barriers, waves will "bounce" off of the barrier in a direction that is constent with the Law of Reflection. In the case of a change in medium, some of the wave reflects while the rest moves into the new medium (see refraction). Here is a simple reflection movie. Back to Top Back to Wave Index
Refraction: Descibes the behavior of waves as the pass from one medium to another. Waves will change speed, either slowing up or slowing down, causing a corresponding change in wavelength. With 2-D or 3-D waves, if the waves do not approach the medium in a "head-on" way, part of the wave will change speed before another part and the wave will change its direction of motion (propagation). View a model of refraction using a car (movie). Back to Top Back to Wave Index
Source: Anything that vibrates to create waves. Back to Top Back to Wave Index
Standing Wave: A wave pattern that occurs when a wave reflects back on itself. When the waves have the right frequency the medium continuosly vibrates but the waves do not appear to move along or propagate through the medium. Nodesand Anti-Nodeswill appear along the standing wave. Click here to see a standing wave form on a slinky (movie). Back to Top Back to Wave Index
Transverse: A kind of wave where the medium is disturbed in a direction that is perpendicular to the direction the wave is moving (propagating). Click for a movie showing a transverse wave. Back to Top Back to Wave Index
Trough: The part of a transverse wave that extends below (negative) the rest state of the medium. Click here to see a trough graphic. Back to Top Back to Wave Index
Velocity: The rate at which an object moves. In other words, how far an object moves in a given amount of time (usually meters/sec in physics). Wave velocity is the rate that waves propagate through a medium and is affected by the medium. You can measure the velocity of waves by measuring how far a waves moves and dividing this by the time the wave takes to move that distance. Back to Top Back to Wave Index
Wave: A wave is a moving disturbance that carries energy along with it. Click here to see evidence that waves can carry energy (movie). Back to Top Back to Wave Index
Wavefront: The straight surface of a plane wave, crest or trough. A plane wave moves in a direction that is perpendicular to the wavefronts. Click for a more detailed description. Back to Top Back to Wave Index
Wavelength: The distance between waves. This is usually measured by determining the distance between two identical regions ( crest to crest or trough to trough). Wavelength is affected by the velocity of waves and the frequency of the source producing waves. If velocity and frequency are known, wavelength can be found by dividing Velocity by Frequency. Click here for a graphic. Back to Top Back to Wave Index
