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Topic: Constructive Interference

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	Interference - Wikipedia, the free encyclopedia
		As most commonly used, the term usually refers to the interference of waves which are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
		When a single source interferes with itself, the principle of conservation of energy dictates that the energy "missing" from the darkened regions of an interference pattern where destructive interference has taken place will be found in the brightened portions where constructive interference has taken place.
		However, in general white light is less suited for producing clear interference patterns, as it is a mix of a full spectrum of colours, that each have different spacing of the interference fringes.
	en.wikipedia.org /wiki/Interference (529 words)

	The Physics Classroom
		The interference of sound waves causes the particles of the medium to behave in a manner that reflects the net effect of the two individual waves upon the particles.
		Interference can occur as the result of sound from two speakers meeting at the same location as well as the result of sound from a speaker meeting with sound reflected off the walls and ceilings.
		When constructive interference occurs, a loud sound is heard; this corresponds to a peak on the beat pattern (drawn in green).
	www.physicsclassroom.com /Class/sound/U11L3a.html (2415 words)

	Light Waves and Color Review - Answers to Q#1-11
		Interference of two waves at a given location results in the formation of a new wave pattern which has a greater amplitude than either of the two interfering waves.
		The only way for two waves to interfere constructively is for a crest to meet a crest or a trough to meet a trough.
		When the displacements of the two interfering waves are in the same direction at a given point, then constructive interference occurs at that point.
	www.glenbrook.k12.il.us /gbssci/phys/chemphys/reviews/u5review/u5ans1.html (2959 words)

	Interference of Waves
		Constructive interference is observed when a crest meets a crest; but it is also observed when a trough meets a trough as shown in the diagram below.
		In this case, a sine trough with an amplitude of -1 unit (negative means a downward displacement) interferes with a sine trough with a displacement of -1 unit.
		In actuality, the task of determining the complete shape of the entire medium during interference demands that the principle of superposition be applied for every point (or nearly every point) along the medium.
	www.glenbrook.k12.il.us /gbssci/phys/Class/waves/u10l3c.html (1340 words)

	The Physics Classroom
		For example, the interference of a crest with a trough is an example of destructive interference.
		Interference principles were first introduced in Unit 10 of The Physics Classroom.
		Whenever light constructively interferes (crest meets crest or trough meets trough), the two waves act to reinforce one another and to produce a "super light wave." On the other hand, whenever light destructively interferes (crest meets trough), the two waves act to destroy each other and produce no light wave.
	www.physicsclassroom.com /Class/light/U12L1b.html (1558 words)

	Olympus Microscopy Resource Center: Light and Color - Interference
		Thomas Young was a early 19th century physicist who demonstrated interference showing that light is a wave phenomenon and who also postulated that different colors of light were made from waves with different lengths.
		Interference intensity distribution fringes (such as those observed in Young's double slit experiment) vary in intensity when they are presented on a uniform background.
		Interference also occurs with sound waves and waves induced in a standing pool of water.
	www.olympusmicro.com /primer/lightandcolor/interference.html (1617 words)

	Diffraction and interference
		The bright fringe in the middle of the diagram above is caused by constructive interference of the light from the two slits traveling the same distance to the screen.
		If the interference pattern is viewed on a screen a distance L from the slits, then the wavelength can be found from the spacing of the fringes.
		The bright fringes, which come from constructive interference of the light waves from different slits, are found at the same angles they are found if there are only two slits.
	electron9.phys.utk.edu /phys136d/modules/m9/diff.htm (1293 words)

	Wave Interference (Site not responding. Last check: 2007-10-02)
		Constructive interference occurs when the wave amplitudes reinforce each other, building a wave of even greater amplitude.
		Regions of constructive interference are labeled with "C" and regions of destructive interference with a "D." Note that the regions alternate, but are not necessarily equal in size.
		Within a standing wave, regions of constructive interference are called antinodes and regions of destructive interference are called nodes.
	online.cctt.org /physicslab/content/Phy1/lessonnotes/waves/lessoninterference.asp (463 words)

	Thin-film interference (Site not responding. Last check: 2007-10-02)
		Constructive and destructive interference of light waves is also the reason why thin films, such as soap bubbles, show colorful patterns.
		This is known as thin-film interference, because it is the interference of light waves reflecting off the top surface of a film with the waves reflecting from the bottom surface.
		An important consideration in determining whether these waves interfere constructively or destructively is the fact that whenever light reflects off a surface of higher index of refraction, a 180° phase shift in the wave is introduced.
	physics.bu.edu /py106/notes/Thinfilm.html (662 words)

	Interference of Sound
		If their amplitudes add, the interference is said to be constructive interference, and destructive interference if they are "out of phase" and subtract.
		Interference has far reaching consequences in sound because of the production of "beats" between two frequencies which interfere with each other.
		If you strike a tuning fork and rotate it next to your ear, you will note that the sound alternates between loud and soft as you rotate through the angles where the interference is constructive and destructive.
	hyperphysics.phy-astr.gsu.edu /hbase/sound/interf.html (281 words)

	Constructive and Destructive Interference
		Constructive interference happens at all frequencies for which an exact integer number of periods fits in the delay line, i.e.
		On the other hand, destructive interference happens at all frequencies for which the number of periods in the delay line is an integer plus a half, i.e.
		It is quick to verify that frequencies of constructive interference alternate with frequencies of destructive interference, and therefore the amplitude response of an LTI filter is simply the magnitude of the (complex) frequency response — Click for http://ccrma.stanford.edu/~jos/filters/Amplitude_Response_I_I.html')">amplitude response of the comb filter (a plot of gain versus frequency) looks as shown in Fig.
	ccrma-www.stanford.edu /~jos/mdft/Constructive_Destructive_Interference.html (519 words)

	No Title
		Thus, whether interference is constructive, destructive, or in between, it is the same, giving the same intensity (or brightness), at every point on the slide.
		At it increases, it passes through a point of constructive interference (where the path difference is), then a little later through a point of destructive interference (with path difference).
		This cycle of constructive then destructive interference repeats many times as we raise slide A, so that we see a uniform field which brightens (constructive interference) and darkens (destructive interference) as we raise slide A. (b) Again light reflecting from the bottom of slide A and from the top of slide B interfere.
	www.emory.edu /PHYSICS/Faculty/Benson/142/mcat9/mcat9.html (882 words)

	Outline - Physical Optics - Physics 106
		Constructive interference occurs when a crest falls on a crest and a trough falls on a trough.
		For constructive interference, the path difference must equal an integral number of wavelengths.
		represents the distance on the screen from center of the intensity pattern to a position of constructive or destructive interference and L the distance from the slits to the screen.
	www.wellesley.edu /Physics/phyllisflemingphysics/106_o_physoptics.html (1729 words)

	Interference of water waves
		Constructive interference occurs at a point when the two waves arriving there are vibrating in the same direction (in phase).
		Destructive interference occurs at a point when the two waves arriving there are vibrating in the opposite directions (anti-phase).
		Any waveforms arriving the two red dots will later arrive P simualtaneously (same length, same speed), hence the relationship between the vibrations (in phase, antiphase or others) of the two red dots will be exactly the same as that of the two waves superposing at P.
	www.ngsir.netfirms.com /englishhtm/Interference.htm (329 words)

	Interference and Diffraction (Site not responding. Last check: 2007-10-02)
		The central region of constructive interference is known as the central maximum, or A
		Another way to change the amount of interference produced by two in-phase point sources is to change their frequency but leave their separation distance unchanged.
		Young’s interference experiment, along with the diffraction effects seen in Fresnel's prediction and the subsequent demonstration by Dominique Arago of Poisson's Spot, showed that light DID have a wave nature.
	online.cctt.org /physicslab/content/phyapb/lessonnotes/twosourceinterference/doubleslitinterference.asp (1384 words)

	Interference
		The result of adding two waves of the same frequency depends on the value of the phase of the wave at the point in which the waves are added.
		To explain the origin of the interference pattern, consider the distance traveled from the two sources.
		Instead, when the difference in pathlength is equal to a wavelength, constructive interference occurs.
	members.tripod.com /~vsg/interfer.htm (241 words)

	Interference
		The interference pattern was a set of alternating bright and dark lines, corresponding to where the light from one slit was alternately constructively and destructively interfering with the light from the second slit.
		You might think it would be easier to simply set up two light sources and look at their interference pattern, but the phase relationship between the waves is critically important, and two sources tend to have a randomly varying phase relationship.
		Applying this to the two slits, each slit acts as a source of light of the same wavelength, with the light from the two slits interfering constructively or destructively to produce an interference pattern of bright and dark lines.
	physics.bu.edu /~duffy/PY106/Interference.html (999 words)

	No Title (Site not responding. Last check: 2007-10-02)
		In order to observe interference, we need the waves to have the same wavelength and to be in a well defined phase relation : the meeting of two waves that are perfectly in phase (i.e.
		From what we have seen, it is clear that, in a given situation constructive of destructive interference will be affected by 1) the thickness of the layer, 2) the light wavelength 3) the angle of light incidence.
		Similarly there will be a family of exit angles for which fully constructive interference occurs, and once again the image of a slit on a remote screen will be a succession of bright and dark bands.
	landau1.phys.virginia.edu /classes/202.sc2k.spring03/chap27/chap27.html (1484 words)

	Interference in thin films
		In everyday life, the interference of light most commonly gives rise to easily observable effects when light impinges on a thin film of some transparent material.
		For instance, the brilliant colours seen in soap bubbles, in oil films floating on puddles of water, and in the feathers of a peacock's tail are due to interference of this type.
		The two beams produce either destructive or constructive interference, depending on whether their path difference is equal to an odd or an even number of half-wave-lengths, respectively.
	farside.ph.utexas.edu /teaching/302l/lectures/node137.html (477 words)

	Study the interference of light using Helium - Neon Diode Laser.
		These are interference bands or interference fringes, the bands disappear when one of the slits A or B is covered.
		The appearance of the fringes is due to the interference of light.
		The dots represents positions of constructive interference, where crest of on wave falls on the crest of other and the trough on trough.
	www.coursework.info /i/69234.html (748 words)

	Interference in two dimensions
		Because the wave lengths and hence frequencies of waves from the two sources have been chosen to coincide the interference pattern will look alike at all times with regions of constructive interference containing propagating waves and regions of destructive interference remaining calm.
		The crux of the matter is that constructive interference will occur if the distance back to the source points differ by an integer number of wave lengths because then the crests and troughs will coincide.
		Destructive interference on the other hand will occur if the difference in distance is half a wave length plus any integer number of wave lengths.
	www.pha.jhu.edu /~broholm/l30/node3.html (497 words)

	Dolores Gende: PhysicsQuest : WAVE BEHAVIOR
		Explain constructive interference of two sound waves in terms of pressure variations.
		A friend tells you that the word destructive tends to imply that the energy as well as the form of the waves is destroyed.
		Another type of interference occurs when the waves are out of phase i.e.
	physicsquest.homestead.com /quest11ac2.html (410 words)

	The Tom Bearden Website (Site not responding. Last check: 2007-10-02)
		The chart is stylized since we assume two single-frequency EM waves which intersect and interfere in the indicated region.
		In the interference zone, in-phase wave amplitudes add (constructive interference) while out-of-phase wave amplitudes subtract (destructive interference).
		Actually the regions of destructive EM interference are regions of constructive G-interference, and the regions of constructive EM interference are regions of destructive G-interference.
	www.cheniere.org /books/ferdelance/s37.htm (146 words)

	Using Bubbles to Learn about Light Interference
		Interference is the addition, or coming together, of several waves.
		Review with students what intereference is. We get interference from a thin film like a bubble, because the light waves which bounce off the front and back surfaces of the bubble wall add constructively or destructively.
		Well, since the color of the fringes (and also their spacing) is related to the thickness of the film, we can use this to measure the thickness of films, which are too thin to measure with, say, a ruler.
	www.reachoutmichigan.org /funexperiments/agesubject/lessons/bubbles.html (929 words)

	July 2000 Newsletter
		If waves are phased with their crests aligned, they are said to have constructive interference, and if a wave's crest is aligned with another wave's trough, they are said to be destructively interfering.
		To see destructive interference and constructive interference at the same time, you can take two screen door screens and lay one over the other.
		If the space between the glasses is a multiple of 1/2 wave then the light had to go 1/2 wave down then 1/2 wave up for a total of 1 wave, which is constructive, or multiples of 1 wave which are constructive.
	astro.sci.uop.edu /~sas/Newsletter/TTN_Fringe.html (1512 words)

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