Questions tagged [interference]

Interference describes different waves superposing to form a resultant wave of greater, lower, or the same amplitude. Normally, it involves interaction of waves that are correlated (coherent) with each other, either because they come from the same source, or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, e.g., light, radio, acoustic, surface, or matter waves.

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Interaction of two sound emitting particles in a medium

Consider a particle freely suspended in a medium. The particle is free from any external forces and so is at rest. Also, consider the medium to be infinite in all directions. If that particle becomes ...
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Momentum and photon indistinguishability

Suppose two photons have the same frequency and polarization, and their wavepackets also have identical temporal and spatial (along their propagation directions, respectively) profiles. The two ...
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How is Electromagnetically-Induced Transparency a result of “destructive quantum interference between two pathways”?

It has been described that Electromagnetically-Induced Transparency (EIT) is a result of "destructive quantum interference between two pathways." To quote from this source: In these simple ...
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How sensitive is double-slit result to a fixed wavelength?

I was watching a video on the double-slit experiment, and the lecturer (*) mentioned, in passing, that the frequency of the waves must be kept the same. (Still in the context of water waves at this ...
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Interference and superposition of waves

In the picture above, black and blue lines are representing waves(mechanical) emerging from the slits(after diffraction). Let us consider that at point A, centre of a bright fringe is located. That ...
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Can someone explain to me why the fringes would move apart in this air wedge?

Consider two identical microscope slides in air illuminate by monochromatic light as shown below. A pattern of interference fringes is formed. If the wedge angle gets smaller, the fringes move further ...
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Visualizing topological deformation and quantum mechanical interference

In section VI.1 of Zee's QFT, he says that for indistinguishable hard core particles in 2D, when comparing trajectories with different winding numbers: Since the classes cannot be deformed into each ...
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Michelson Interferometer with expanding glass rod

So I've been working on this question for a while and am still no further at finding an answer. I'm probably just approaching this wrong, I'm at a loss for ideas though. "The index of refraction of a ...
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Making equal arguments of sine or cosine function

I have trouble understanding one common type of inference about waves. In physics textbooks, frequently when text is about waves I see inference where arguments of trigonometric functions made equal ...
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Interference pattern due to a thin prism and a lens

We have a setup like this where a converging lens placed between inclined face of thin glass wedge and a screen. The screen is parallel to the inclined face of the wedge and the optical axis of the ...
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Interference of two phase-modulated photons

Results about the quantum mechanical formulation of single-photon Mach-Zehnder set-up are already accessible. However, it is not obvious how two photons interfere when we have applied an arbitrary ...
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Diffraction Grating question/s

I wrote a little program to model a diffraction grating: Does a photon go thru every slit, or just a few, in an inch/es wide DG!? Do I treat a slit as just a single point source? Does a photon ...
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Introducing two different slabs in Young's double slit experiment

Suppose there are two slabs of refractive indices $n_1$ and $n_2$ kept in front of the sources of light with wavelength λ as shown, how do we calculate the distance of the first bright fringe from the ...
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What determines how much power goes into each diffraction order?

Imagine a grating with infinite number of slits, and the spacing D between slits is larger than the wavelength so that there are high order diffractions. In each of the diffraction directions the ...
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Matter wave coherence length

Coherence length is defined as (see here) The propagation distance over which a coherent wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Other questions see here, and ...
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Why does diffraction happen in cases like these?

Diffraction, at least as its commonly explained, happens when light crosses an obstacle "of size in the same order as its wavelength". For example, a small slit. However, in one of my labs, ...
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Effect of finite width of source slit, diffraction?

I am studying Fraunhofer diffraction on Jenkins And White Fundamentals of Optics. The apparatus is and in one chapter he considered $S'$ of finite width and they consider two source points $P$ and $...
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What does it mean for a light to have low-coherence?

I've been searching about OCT imaging and understood that it is based on low-coherence light source. The problem is, I don't understand what is a low-coherence light source. Based on what points that ...
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Amplitude modification in double slit interference

Over the surface of interference, illumination varies. We have calculated so perfectly about it so that we know exactly how the variation chart looks like. Even our vision renders it as in that chart. ...
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Do slits cause light to become coherent?

In the young double slit experiment, you have a single slit followed by two slits. I believe it is the single slit which cause the light to diffract and become coherent and the double slit is to ...
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How can reflected light be visible if for every trough of a light wave, there is also a simultaneously arriving peak?

When monochromatic light is emitted from a source, there are many out of phase waves. As these waves arrive a place on a screen, there are a multitude of phases. As this is not 'coherent light', their ...
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What is the intuitive reasoning behind a factor of 4 in the Fraunhofer double-slit intensity equation?

For Fraunhofer diffraction, the intensity of a single-slit setup obeys $I(\theta) = I_{o}\left [\frac{\sin(\frac{\pi a}{\lambda}\sin\theta)}{\frac{\pi a}{\lambda}\sin\theta} \right ]^2$. where $a$ is ...
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Diffraction grating of light

Although I could understand the basics of single slit diffraction, diffraction grating seems something confusing to me. In diffraction grating, we know there are a lot of slits within a unit length. ...
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Is, in the “double point-source experiment”, an interference pattern visible in the vertical direction?

A double-slit experiment is performed where the slits are replaced by small circular apertures with a very small diameter (compared to the distance to the screen). An interference pattern is observed ...
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The Feynman Lectures on Physics Interference

From The Feynman Lectures on Physics, Feynman states that: You will remember that the quantitative relationship between I1, I2, and I12 can be expressed in the following way: The instantaneous height ...
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Is there a difference between a diffraction pattern and an interference pattern?

I am in high school at the moment and I am revising a section on waves. I am slightly confused by some things in our notes, which I would like to ask about. We looked at Young’s double slit experiment,...
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Isn't the formula and definition of fringe width given by my book wrong?

The definition of fringe width given by my book can be understood from this figure. According to Byju's, the distance between two consecutive bright or dark fringes is called the fringe width: this ...
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Interference pattern vertical or horizontal

in a double slit experiment, if the 2 slits are horizonal, the interference pattern will be of horizontal lines. But what about if the 2 slits are point sources. Will the interence pattern be ...
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Multiple beam reflection and sharp fringes

Why multiple beam reflection method interferometry produces sharp fringes? I came across this assertion while reading Fabry Perot interferometry. But i can't find the justification of it. Can anyone ...
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Why does the intensity of the bright fringes decrease as we move away from the central maxima in Young's Double Slit Experiment?

I studied that in Young's Double Slit Experiment the variation of intensity ($I$) of the fringes on the screen with respect to the phase difference ($Φ$) is given by : $I = 4I_{0} \cos^{2}\frac{Φ}{2}$ ...
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Fresnel biprism experiment - Why is the motion of eyepiece perpendicular to the length of the bench?

Why is the motion of eyepiece perpendicular to the length of the bench? what does this statement mean?
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White light instead of monochromatic light in interference

In a double slit experiment, if monochromatic light is replaced by white light what effect does it have on the fringes. Answer given is below. Can someone please explain the answer.? Central ...
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Does bringing slits closer together increase or decrease intensity of interference pattern

Does bringing the slits together affect the intensity of maxima for double slit experiment and also the diffraction grating? Does decreasing slit width affect the intensity of the maxima for a single ...
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Newton's rings due to two equiconvex lens

An equiconvex lens is placed on another equiconvex lens. The radii of curvatures of the two surfaces of the upper lens are $R_1$ and those of the lower lens are $R_2$. The waves reflected from the ...
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Mach Zehnder classical output [closed]

$E_{0}$ is input to the first beam splitter and the output from the first beam splitter: $|E_{0}|^2=|E_{1}|^2+|E_{2}|^2$ $E_{1} = \frac{E_{0}}{\sqrt{2}}\;sin( \omega t - kx)$ $E_{2} = \frac{E_{0}}{\...
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Why does intensity decrease from the centre fringe in slit experiments?

This happens in double slit, single slit and grating experiments with light. Looking for an intuitive answer.
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Does the material of the screen affect the interference pattern of the electrons in the double-slit experiment?

The question comes from thinking about the way how the screen material affects the interference pattern. Let's say that half of the screen was from one material and the other half from different ...
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Noise Cancellation - Destructive Interference

We know that active noise cancelling headphones work by playing a signal in your ear which is 180º out of phase with the ambient noise. If we compare the two waves, the peak in one wave is completely ...
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Causality and wave configurations in dispersive media

As motivation, consider if I handed you two photographs of a ball at two different times, and asked you if it were possible for the ball to have traveled as far as it did in a certain time. In the ...
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How does light interference explain colour mixing? [duplicate]

I've grown curious about the phenomenon of light interference. If two light sources of different wavelengths that correspond to two arbitrary colours, say blue and yellow, constructively join, they ...
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Interference in a light clock (with a laser), moving perpendicular to the light

Starting with the typical light-clock setup, but replacing it with a laser, it is possible to tune the distance between the mirrors so that the light destructively interferes with itself on the return ...
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Fresnel biprism little concepts

For a Fresnel biprism can anyone please tell how to prove that the distance between the virtual image sources formed is 2a(n-1)α . I can't find any resource where can I understand the derivation. Most ...
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Why do we use a microscope to observe newton's ring? Can short focal distance telescope be used instead?

In newtons ring experiment we place the lens setup below a microscope which is then moved vertically until the fringes can be seen. In case of Determination of Cauchy's constants, we use a ...
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How to know the true value of the measured quantity from an interferometer phase?

For an interferometer, the measured signal will oscillate as a function of the accumulated phase $\phi(x)$ as a sinusoid or cosine, where $x$ is a quantity we are trying to measure from the ...
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Why do we observe the difference in the intensity pattern of Interference and Diffraction?

As well said by Richard Feynman, “No one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a question of usage, and there is no specific, ...
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Double source (not slit) interference pattern

In this question, I assumed that the two sources should act like the two slits in the Double Slit Experiment, and give a graph similar to this: However, as per the markscheme, the intensity graph is ...
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Amplitude distribution in reflection and transmitted waves

Let us consider an incident wave $y_i$ travelling along positive x-axis in medium $1$ which is reflected($y_r$) and refracted(transmitted)($y_t$) across the boundary(at $x=0$) between medium $1$ and ...
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About two photon interference in nanophotonics

Within the standard model, photons are point particles, i.e., with no spatial distribution. On the other hand, classical electromagnetic modes have field distributions. Suppose there are two different ...
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White light interferometer

I am building white-light Michaelson interferometer and I am registering interference in frequency domain via spectrometer. I read an article, where the same is done (just Mach-Zender interferometer) ...
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Single slit diffraction angle between maxima

Lets say we have a certain wavelength $\lambda$ and a known slit width $d$, how can I calculate (approximately) the angle $\theta$ between the central maxima and the next maxima? I know that $d \sin \...

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