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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.

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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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 polarizations) meet at a point such that they're 180…
user22862
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What happens to the energy when waves perfectly cancel each other?

What happens to the energy when waves completely cancel each other out via destructive interference? It seems like the energy just disappears, but that would violate the law of energy conservation. My guess is that the kinetic energy is transformed…
aortizmena
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Why don't choir voices destructively interfere so that we can't hear them?

Sound is propagated by waves. Waves can interfere. Suppose there are two tenors standing next to each other and each singing a continuous middle-C. Will it be the case that some people in the audience cannot hear them because of interference?…
chasly - supports Monica
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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 thinking; please tell me where I am mistaken. Say…
bitsmack
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What causes this pattern of sunlight reflected off a table leg?

My friend noticed an interference-like pattern around the table leg. However, we do know that interference patterns of sunlight produces rainbow colours. What seems to be happening here?
Luke
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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 somewhat perplexing, since AFAIK it's pretty common to…
user4552
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If a thousand people whisper inaudibly, will the resulting sound be audible?

If a thousand people whisper inaudibly, will the resulting sound be audible? (...assuming they are whispering together.) I believe the answer is "yes" because the amplitudes would simply add and thus reach an audible threshold. Is this right? if…
SAH
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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 interferes with itself. Different photons (for example from…
Kostya
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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 visor and a placeholder for a microscope slide with…
AnimatedPhysics
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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?
Abdul Wajid Lakhani
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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 in the above animation reaches your ear a few…
Daniel M.
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Why does light reflected from an LED TV screen make a sharp X pattern?

If you shine a laser pointer or generally any coherent light at the screen of a fancy, new TV, you get a very sharp X pattern. I think this is a property of LED screens specifically. This phenomenon has been noted many times (1, 2, 3, 4), but…
knzhou
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Double slit experiment at home failed

At night, I went outside. I had a box with two slits in it. I directed torch light towards it, but I saw only two bands of light on the wall and shadow from the rest of the box. Why did it not produce interference like a double slit experiment…
Apple_Banana
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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 spectrum. I don't understand how this works. Shouldn't…
Black Dagger
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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 proportional to $2A^2$. When they interfere, the…
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