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Lecture

Interference: Wave Superposition

In course

PHYS-201(c): General physics : electromagnetism

Introduction à la mécanique des fluides, à l'électromagnétisme et aux phénomènes ondulatoires. ...

Description

This lecture covers the interference phenomenon, which occurs when waves from nearby sources superimpose. It explains how interference arises from the superposition of waves, leading to the formation of interference fringes. The lecture delves into the Young interference experiment with photons, highlighting the challenges of achieving coherence between sources. It also discusses temporal and spatial coherence, coherence time, and coherence length, emphasizing the correlation of phase in light waves. The concept of interference from two coherent sources is explored, detailing constructive and destructive interference patterns. Additionally, the lecture addresses the interference of waves emitted by neighboring sources and the conditions required for interference to occur.

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Instructor

Giovanni Boero

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Related concepts (32)

Wave interference

In physics, interference is a phenomenon in which two coherent waves are combined by adding their intensities or displacements with due consideration for their phase difference. The resultant wave may have greater intensity (constructive interference) or lower amplitude (destructive interference) if the two waves are in phase or out of phase, respectively. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves, gravity waves, or matter waves as well as in loudspeakers as electrical waves.

Coherence (physics)

In physics, coherence expresses the potential for two waves to interfere. Two monochromatic beams from a single source always interfere. Physical sources are not strictly monochromatic: they may be partly coherent. Beams from different sources are mutually incoherent. When interfering, two waves add together to create a wave of greater amplitude than either one (constructive interference) or subtract from each other to create a wave of minima which may be zero (destructive interference), depending on their relative phase.

Wave

In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (resting) value at some frequency. When the entire waveform moves in one direction, it is said to be a traveling wave; by contrast, a pair of superimposed periodic waves traveling in opposite directions makes a standing wave.

Transverse wave

In physics, a transverse wave is a wave whose oscillations are perpendicular to the direction of the wave's advance. This is in contrast to a longitudinal wave which travels in the direction of its oscillations. Water waves are an example of transverse wave. A simple example is given by the waves that can be created on a horizontal length of string by anchoring one end and moving the other end up and down. Another example is the waves that are created on the membrane of a drum.

Coherence length

In physics, coherence length is the propagation distance over which a coherent wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Wave interference is strong when the paths taken by all of the interfering waves differ by less than the coherence length. A wave with a longer coherence length is closer to a perfect sinusoidal wave. Coherence length is important in holography and telecommunications engineering. This article focuses on the coherence of classical electromagnetic fields.

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