# 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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### What happens to the energy when waves perfectly cancel each other?

What happens to the energy when waves perfectly cancel each other (destructive interference)? It appears that the energy "disappear" but the law of conservation of energy states that it can't be ...
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### Is coherent light required for interference in Young's double slit experiment?

In this Veritasium video, a home experiment is presented which appears to produce a very good double-slit interference pattern with normal sunlight. The experiment is an empty cardboard box with a ...
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### Energy conservation and interference

I have a problem with energy conservation in case of interfering waves. Imagine two harmonic waves with amplitudes $A$. They both carry energy that is proportional to $A^2$, so the total energy is ...
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### Relationship between the material properties of an edge and the fringes behind this edge

The double-slit experiment shows fringes on a screen. Closing one of the slits there is still an interference pattern on the screen behind the slit. Making the slit wider we still see fringes between ...
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### Why is Huygens' principle only valid in an odd number of spatial dimensions?

Apparently Huygens' principle is only valid in an odd number of spatial dimensions: https://mathoverflow.net/a/5396/21349 Huygen's principle in curved spacetimes Why is this? [EDIT] This is ...
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### Why must the single slit in a double slit experiment be narrow?

I read that this causes contrast to become lost between dark and light fringes, but why?
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### Does a photon interfere only with itself?

I sometimes hear statements like: Quantum-mechanically, an interference pattern occurs due to quantum interference of the wavefunction of a photon. The wavefunction of a single photon only ...
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### Fully destructive interference

I'm aware that this is somewhat of a frequently asked question (not only here), and i've dug through respective answer for a few hours before i decided to ask here. None of those answers helped me ...
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### How does light know which path is fastest?

We know from Fermat's principle of least time that light follows the fastest path. But how does light know which path is the fastest?
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### How much red, blue, and green does white light have?

Different kinds of white light have a different spectrum. Light from a white LED will have blue at the peak intensity while white light from a CFL or something else will have a different looking ...
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### Fringe width and spacing and number of slits in diffraction experiments

In a single slit experiment, the fringes are not equally spaced and aren’t of equal widths—the central maximum is the widest, the secondary maxima grow narrower and narrower outward, and the minima ...
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### Are double-slit patterns really due to wave-like interference?

According to various sources on the web, it seems like the general concensus is that there isn't actually any wave-particle duality with quantum particles. For example, this article implies that ...
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### How does Huygens Principle incorporate the unidirectional property of a traveling wave?

I was reading French's Vibrations & Waves where he discusses Huygens-Frensel Principle. The principle talks about how secondary sources give rise to secondary wavelets to form the displaced ...
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### Michelson interferometer circular fringes

Image source I have never done the experiment so as far as I understand, if the mirrors $M1$ and $M2$ are perpendicular to each other the observer at $O$ will see a circular fringe pattern. If ...
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### Shooting a single photon through a double slit

Consider the image below. It shows a double slit experiment but with a single photon at a time. My question is as follows: Why is it that the photons always take a different path when shot at the ...
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### Young's double split experiment, the slit width

I realize that there is a lot of topic's mentioning this, but I think my question is rather new compared to many of them. First of all, this is part of a school assignment, and our object is to ...
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### Interference at the focus of a convex lens or a concave mirror

Now consider parallel rays travelling towards the convex lens. After emerging they get converged at the focus. Won't this lead to interference between light rays? Practically it should but I would ...
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### Why do we actually see the sun?

I haven't yet gotten a good answer to this: If you have two rays of light of the same wavelength and polarization (just to make it simple for now, but it easily generalizes to any range and all ...
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### Single Photon Single Slit Interferometry

If just a single photon hit a single slit interferometer, what would happen? Would you just see a dot on the screen, or would there be a diffraction pattern? Furthermore, if you had a double slit ...
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### Recently publicized experiment on destructive interference between two laser beams

Recently I've had several non-physicist friends ask me, independently of each other, about an experiment where two collinear laser beams destructively interfere along a certain length. Everybody wants ...
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### Which is the biggest object which can interfere with itself?

I've heard that scientist proof that viruses of the Tobacco mosaic virus could interfere with themselves. I'm referring to quantum interference-- the same as photons. Unfortunately, I couldn't find ...
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### Intensity of subsidary maxima in a diffraction grating pattern?

I was wondering if anyone knew what the intensity of subsidary maxima was? My intuition would tell me that it would be the square of the amplitude of the wave illuminating the slits (I am thinking ...
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### What was Newton's own explanation of Newton's rings?

What was Newton's own explanation of Newton's rings? Newton advocated a corpuscular theory of light, but his rings would most conveniently be explained by a wave theory. How did he explain his own ...
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### Do interference rings disappear in an interferometer if the path lengths are identical?

Consider a standard Michelson Interferometer (I took the picture from http://en.wikipedia.org/wiki/Interferometer) The incident beam is split into two parts, where the two parts travel on different ...
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### How does interference move energy from destructive to constructive regions?

I recently read (sorry but I don’t have a reference) that interference is not only about destructive and constructive interference but moving energy from destructive to constructive regions according ...
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### Why is it difficult to differentiate between interference and diffraction?

Why is it difficult to differentiate between interference and diffraction? Is it because we don't clearly understand how both of these phenomenon takes place? My thoughts: From an answer to one of ...
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### Does wave interference happen only to same frequency waves?

As the title says, from books and results from internet, I find that examples of wave interference always have the same frequency, only different in phase constant. So, I'd like to know if wave ...
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### Why don't waves with different wavelengths interfere with each other in white-light?

The book I'm reading about optics says at some point that "each color (wavelength) contained in the white light interferes only with itself". But why is this so? Edit: I moved the rest of the ...
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### How is the width of a slit related to the intensity of light passing through it?

Here's a question I got in my final exam this morning. "If in Young's double-slit experiment setup, the ratio of the intensity of the bright spot to the dark spot is 25:9, what is the ratio of ...
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### reproducing double-slit experiment with sunlight

Is it possible to reproduce Double-slit experiment at home with sunlight probably in a larger scale? Thanks for all the answers (and special thanks to Chris for the effort),so i understand that it ...
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### Single photon and double-slit experiment [duplicate]

Laser fires single particles of light, called photons, through the slits. Even though only single photons of light are being fired through the slits and They create three pattern again. How single ...
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### What is the difference between diffraction and interference of light?

I know these two phenomena but I want to know a little deep explanation. What type of fringes are obtained in these phenomena?
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### Difference Between Fraunhofer and Fresnel Diffraction

What is the difference between Fraunhofer diffraction and Fresnel diffraction? I mean diffraction is just bending of light waves or waves in general around a point. So how can there be two types of ...
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### How come an anti-reflective coating makes glass *more* transparent?

The book I'm reading about optics says that an anti-reflective film applied on glass* makes the glass more transparent, because the air→film and film→glass reflected waves (originated from a paraxial ...
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### Does diffraction occur before interference?

In the double slit experiment, light passes through two slits and the waves interfere and form an interference pattern. A single slit is required for diffraction. So, I was thinking about whether ...
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### Interference of polarized light

Does polarized light interfere?
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### Diffracton at the edges of an opaque object?

To understand the phenomenon of diffraction as an interference effects of several dipole oscillators (like in case of several symmetrical, not sawtooth, scratches in a diffraction grating), we ...
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### How come unpolarized light does not undergo destructive interference?

As far as I know, unpolarized light is defined as light which has no clear axis of polarization, but electric field vectors in all directions. However, I also know that electric fields can be ...
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### How light from a thermal source gets coherent behind a small hole?

To this question Why are there interference patterns from black body radiation? was given a statement: Incoherent light going through a small hole creates coherence, and that is how Young got ...
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### Where does energy go in destructive interference? [duplicate]

I have read that when two light waves interfere destructively, the energy contained within is transferred to other parts of the wave which have interfered constructively. However, I am having some ...
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### Do laser beams interfere noticeably with each other?

I want to arrange some red lasers along a 90 degree arc of a circle, aimed towards the center of the circle. When their beams hit the opposite side of the circle, will I notice any interference ...
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### How does Huygens Principle explain interference?

How exactly does Huygens theory about the propagation of wavefronts account for interference?
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### Destructive interference and energy conservation

In case of interference, we know, energy is neither destroyed, nor created; but only redistributed. But in the case of an extremely thin film, due to a reflection and hence a phase difference of $\pi$,...
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### Why don't photons interfere/interact with one another, as common mechanical waves would?

After all, they are a (self-sustaining) perturbation of the same field, like sound waves or water waves are "energy flow" (except these ones experience dissipation). And how can our eyes be ...
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### Why don't two musical instruments sometimes generate destructive interference?

I'm an electrical engineer, and I understand wave propagation, interference patterns, and so on. But I'm missing something basic, so perhaps my understanding isn't as good as I believe. I'll show my ...
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### If two sound waves that are different frequencies create beats that occur several hundred times per second, can you hear this effect as its own tone?

If you have multiple waves of different frequencies, the interference from the different waves cause "beats". (Animation from https://en.wikipedia.org/wiki/Group_velocity) Let's say that a green dot ...
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### Why does a wave actually diffract?

I know that waves diffract around a slit and this is due to the Huygens-Fresnel principle. But I never understand this in an intuitive wave that why does a wave become a spherical wave front at the ...
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### Why does the interference pattern change with given relation when the source slit changes?

Why should the dependence relation be like $${\frac{s}{S}}<{\frac{\lambda}{d}}$$ for the interference condition to be seen? Where $s$ is the width of the source slit and $S$ is the distance ...
Why is there interference present between the two pulses when looking at the spectrum, if they clearly do not overlap in time, and assumingly in space as well (since $x=ct$)? The spectrum is detected ...