Interference
Interference occurs when multiple waves interact with each other, and is a change in amplitude caused by several waves meeting.
Learning Objective

Contrast constructive and destructive interference
Key Points
 Interference is a phenomenon of wave interactions. When two waves meet at a point, they interfere with each other.
 There are two types of interference, constructive and destructive.
 In constructive interference, the amplitudes of the two waves add together resulting in a higher wave at the point they meet.
 In destructive interference, the two waves cancel out resulting in a lower amplitude at the point they meet.
Terms

coherent
Of waves having the same direction, wavelength and phase, as light in a laser.

amplitude
The maximum absolute value of some quantity that varies.

displacement
A vector quantity that denotes distance with a directional component.
Full Text
Unlike solid objects, two waves can share a point in space. In physics, interference is a phenomenon in which two waves (passing through the same point) superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other (i.e, "interfere" with each other), either because they come from the same source or because they have the same or nearly the same frequency.
The effects of interference can be observed with all types of waves, for example, light, radio, acoustic and surface water waves . The idea that interference is caused by superposition means that when two waves meet their two amplitudes (their maximum absolute value) combine together.
Interference
Two overlapping waves exhibit interference.
Interference can be constructive or destructive. In constructive interference, the two amplitudes of the waves add together and result in a higher displacement than would have been the case if there were only one wave. An example of constructive interference may be seen in .
Constructive Interference
Pure constructive interference of two identical waves produces one with twice the amplitude, but the same wavelength.
Destructive interference is when two waves add together and the result is a smaller displacement than would have been the case. An example of destructive interference can be seen in . When the waves have opposite amplitudes at the point they meet they can destructively interfere, resulting in no amplitude at that point. For example, this is how noise cancelling headphones work. By playing a sound with the opposite amplitude as the incoming sound, the two sound waves destructively interfere and this cancel each other out.
Key Term Reference
 constructive interference
 Appears in these related concepts: Spherical and Plane Waves, Young's Double Slit Experiment, and Standing Waves on a String
 destructive interference
 Appears in these related concepts: Newton's Rings, Reflections, and ParticleWave Duality
 frequency
 Appears in these related concepts: Frequency of Sound Waves, Characteristics of Sound, and Sound
 interfere
 Appears in these related concepts: Beats, Superposition and Interference, and XRay Diffraction
 interference
 Appears in these related concepts: Interference and Diffraction, Holography, and Thin Film Interference
 resultant
 Appears in these related concepts: Adding and Subtracting Vectors Graphically, TwoComponent Forces, and Forces in Two Dimensions
 superimpose
 Appears in these related concepts: Conditions for Wave Interference: Reflection due to Phase Change, Superposition, and Standing Waves and Resonance
 superposition
 Appears in these related concepts: Diffraction, Superposition of Electric Potential, and The Discrete Fourier Transform
 wave
 Appears in these related concepts: Properties of Waves and Light, Waves, and Atomic Structure
 work
 Appears in these related concepts: Heat and Work, Energy Transportation, and The First Law of Thermodynamics
Sources
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