Questions tagged [waves]

Waves are disturbances that propagate through space and time. Classically, they travelled through a medium, disturbing the particles but not changing their mean position. Electromagnetic waves/particle-waves need no medium; they are disturbances in their respective fields.

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Double slit - higher dimensions

The double slit experiment is a real-life manifestation of the Huygens principle. As is well-known, this principle depends on whether the number of dimensions is ever or odd; as Evans1 puts it, ...
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Is Wikipedia wrong about Huygens-Fresnel Principle?

Someone posted a question about why backward waves don't exist according to the Huygens-Fresnel principle: Why doesn't a backward wave exist? In following up on this question I read the ...
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Can ray-tracing be used to design a stealth air craft? Or is it necessary to use wave theory?

This question is inspired/kicked-off by a question over in Aviation SE asking about the design of stealth air craft. Stealth technology is usually referred to when trying to make vehicles invisible ...
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Physical intuition for the solutions of the wave equation

I have been studying the wave equation in $\mathbb{R}^n$ for the cases $n=1,2$ and $3$. In the three cases, working all over $\mathbb{R}^n$. That is: $u_{tt}(x,t)=c^2 \Delta_{x} u(x,t)$ for $x \in \...
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Relation between the electric and magnetic fields for an arbitrary electromagnetic wave

When solving the wave equation for electromagnetic waves, $$ \nabla^{2} \mathbf{E}=\mu_{0} \varepsilon_{0} \frac{\partial^{2} \mathbf{E}}{\partial t^{2}}, \quad \nabla^{2} \mathbf{B}=\mu_{0} \...
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Pressure underneath wave

I enjoy water sports and activities in the water. I've swam around and dived down enough to need to equalize my ears and in general have felt water pressure. I've since taken up surfing and have ...
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Numerical Solution of the Propagation-Dispersion equation

I have asked this question on Computational Science and also on Mathoverflow, but no satisfactory answers so far. I thought maybe the physics community could shed some insight on the issue. I am ...
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Confusion regarding Young's double slit experiment in different media

The Problem Consider the given arrangement: Point $P$ is equidistant from $S_1$ and $S_2$ .The glass slab in air has refractive index $\mu_{2}$, and the one in water($\mu_{1}$) has refractive index $...
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Why do scattered waves vanish when the wavenumber of the incident wave is an eigenvalue of the interior Dirichlet problem. Where has the energy gone?

I normally work with numerical computations for wave scattering, but I am now trying get a better understanding of the physical processes underlying the theory, in particular what happens to the ...
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Obliquity factor in Huygens principle

What is the derivation of the obliquity factor (intensity proportional to 1+cosø,where ø is the angle between direction of wave propagation and wavefront tangent at some point on the envelop) used in ...
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On why in transparent media light speed is altered by elastic scattering of photons and their path lengths

I have read this: https://en.wikipedia.org/wiki/Higgs_boson Where it says: "Symmetry breaking in optics In a vacuum, the light of all colours (or photons of all wavelengths) travels at the ...
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Characteristics of wavepackets

I've been learning about wave packets and group velocities recently and had a question. Using simple trigonometric identies, we can show that the super position of two traveling waves with frequency-...
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Boundary conditions for enthalpy waves inside a pipe

So I'm trying to solve a form of the wave equation for sound produced by a vortex distribution $\vec{\omega}$ convecting at velocity $\vec{v}$ . $$\left(\frac{1}{c_0^2} \frac{\partial^2}{\partial t^...
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What's the difference between exchange spin wave and magnetostatic spin wave?

So far I've heard of three kinds of spin waves Magnetostatic spin waves (MSW) Dipole-exchange spin waves (DESW) Exchange spin waves (ESW) What's the difference?
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Is there an explanation for this unexpected similarity between binomial coefficients and waves?

Background Binomial coefficients appeal mostly in probability, combinatorics number theory etc so were were surprised when we observed something that appeared to belong more to physics than pure ...
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How do we know sound pressure squared is proportional to the power in the sound wave?

I am trying to find the equation that explains why we can say the pressure exerted by a wave (squared) is proportional to the power. I see this claim made a lot but I can't tell where it comes from.
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Shield gamma/X-ray/ultraviolet radiation without blocking radio waves

I was theoretically considering building an airtight enclosure that shielded the insides from gamma/X-ray/ultraviolet radiation but did not block radio waves (so that communication would not be ...
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Derive shape of sound wave from vibrating string simulation

I have a physical simulation of a vibrating string (made with matter.js). From this, how can I derive the sound wave / air pressure over time, that would result from such a string? I had considered ...
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Why is the speed of sound wave in a gas always lesser than the r.m.s. speed at the same temperature?

My book says that the speed of sound wave in a gas is always lesser than the r.m.s. speed of the gas at the same temperature. I understand that speed of sound is given by: $$v_s=\sqrt{\frac{\gamma RT}{...
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Why is the intensity function of $N$-slits interference symmetric?

I'm taking a course of quantum physics and we were asked to plot the intensity function of interference between the waves which exit 20 slits, when the distance between the slits is given by $$ d+A\...
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X-ray intensity and the dependence of that intensity on the atomic position

I am currently studying the textbook, Solid-State Physics, Fluidics, and Analytical Techniques in Micro- and Nanotechnology, by Madou. In a section on X-Ray Intensity and Structure Factor $F(hkl)$, ...
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What is electromagnetic radiation (when it is not a 'wave' of EM fields or interacting locally as a photon)?

My questions are related to the question asked at Are EM radiation and EM waves the same thing?. My background is in math (my Ph.D. thesis was in geometric analysis), and I have only taken basic ...
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Can the Taylor expansion of Energy/Intensity be explained more in-depth?

In reference to the question, "Why is energy in a wave proportional to amplitude?" Ben Crowell answered with the answer attached. The original post is linked here. I did not respond to the original ...
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Wave equation on Air- Solid interaction

Suppose that there is, due to an explosion $h$ meters above the ground, a wave in the air with high density, velocity and pressure, capable of inducing an elastic wave on the earth's surface. How does ...
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Can I compute mass of an object in a box based on the sound the object makes when shaken? (Barton Fink movie)

In this movie called "Barton Fink" the main character, Fink, is given a mysterious box with an object inside it, he shakes the box up and down, is it possible to calculate the mass of the object ...
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Boundary condition on $\mathbf{B}$ to describe resonant cavities from waveguides

In Jackson- Classical Electrodynamics when resonant cavities are discussed (8.6, page 252) (but also at page 7 here or at page 19 here) the explanation is made by saying that the solution is the same ...
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Can our eyes and ears detect phase information in addition to amplitude and frequency information?

Both eyes and ears detect continuous waves that impinge upon them - electromagnetic waves in the case of eyes, and sound air pressure waves in the case of ears. The amplitude of these waves is ...
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Quarter wave matching layer of a piezoelectric transducer

I am trying to understand the quarter wave matching between two layers of impedance $Z_1$ and $Z_2$, where $Z_1 > Z_2$. I can understand the electrical transmission line analogy of matching layer ...
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What is the difference between "normal mode" and just "mode"?

So in the oscillation problems, is there difference between "mode" and "normal mode"? I know that "normal modes" are independent and orthogonal, so one doesn't affect the other. Now I am not sure when ...
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Envelope of wavepacket and group velocity

In this answer a possible derivation of the group velocity is provided. It is, anyway, based on the assumption that there will always be a point where all the cosines will sum with the same phase: ...
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Why is phase velocity not a vector and what is the conceptual meaning of "phase slowness"?

I was reading Principles of Optics by Born and Wolf; there they introduced the concept of phase velocity as follows: [...] If we denote $\mathbf q$ the unit vector in the direction of $\mathrm d\...
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What is the difference between microscopic quantum interference between photons and macroscopic interference between laser beams?

To get interference between laser beams we use an interferometer composed of mirrors and one beam splitter. To get interference between photons we use an interferometer composed of polarizers, ...
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Why is the total force at a free surface zero?

I am looking into waves on a free surface for which their are two main conditions: Kinematic condition: Particles on the surface remain on the surface. Dynamic condition: Forces acting on the surface ...
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Distinguishing transverse and longitudinal from wave equation

Can we distinguish if a general wave or disturbance $f$ (not necessarily electromagnetic) which satisfies the wave equation \begin{equation} \frac{1}{v^2}\frac{\partial^2 f}{\partial t^2} = \frac{\...
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Proof that fixed points of a null field are zero

Suppose we have a scalar field $V$ (which can be acoustic pressure, or a scalar electric potential) that is a solution of the wave equation $$\Box V(x,y,z,t) = 0$$ I am wondering if a fixed (non-...
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How to calculate dispersion relation from a Finite Difference (FD) wave simulation

I have a python code that calculates the solution of the inhomogeneous acoustic wave equation for a 2D medium with any velocity and source configuration. It was implemented using Finite Differences ...
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Linear KDV eq. asymptotics

The question arises from the book Solitons by P. G. Drazin about the linearized KDV eq. $$ u_t+u_{xxx}=0 $$ My first step was to take a Fourier transform of the equation, find that the dispersion ...
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Worthington jets explanation: fluid phenomenon

I don't understand the reason behind the formation of Worthington jets I've been reading a bit about Worthington jets Video 1, this phenomenon is caused when something is thrown to the water as we ...
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How to get the pressure amplitude at any spatial point?

Working on the pressure equation from the linearized euler equations, I stumble across a very simple problem : How, from the pressure solution of the specific equation (see http://www.acs.psu.edu/...
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Sound waves and chromism?

I am definitely not a physicist, but I have a question related to Physics so I thought I'd give it a try. Please excuse my ignorance. :) I am somewhat familiar with the changes in color caused by ...
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What criterion did Abbe use?

For a microscope (correct me if I am wrong) the Rayleigh Criterion gives us: $$ R=\frac{1.22 \lambda}{NA_{condenser}+NA_{objective}}$$ But with the Abbe diffraction limit: $$ R=\frac{\lambda}{NA_{...
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Ray tracing a three-way intersection

I've been studying ray tracing in media with linear velocity-depth functions. One of the key concepts I've come across is the ray parameter, and in particular the idea that the ray parameter is ...
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Polarization of a transverse wave travelling in ionosphere with polarization direction perpendicular to earths magnetic field

Assume a transverse electromagnetic wave entering ionosphere such that its electric field is perpendicular to Earth's magnetic field. Now, I read that as it will enter plasma, the wave will tend to be ...
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Chladni Plate Mathematics

I am a high school student doing an IB Extended Essay investigation concerning the resonant frequencies of Chladni plates of differing materials and sizes. Would someone please explain the definition ...
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1answer
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Solving wave equations with Fourier transform: where are the time-independent solutions?

One typically solves waves (fields) equations in Fourier space. For example, the 1D wave equation $\frac{\partial^2\phi(x,t)}{\partial t^2}-\frac{\partial^2\phi(x,t)}{\partial x^2} = 0$ in Fourier ...
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Does diffraction take place in Young's double slit experiment?

In diffraction experiments interference takes place along with diffraction? Does diffraction take place in Young's double slit experiment? If it does take place then why don't we get the pattern of ...
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how can interference occur within diffraction?

My book says : The number of interference fringes occuring in the broad diffraction peak depends on the ratio d/a that is the ratio of the distance between the two slits to the width of a slit. In ...
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Intensity of reflexion of circular polarization

Circularly polarized light, can be caracterized as : $$E(r,t) = E_0 \cos(kz-\omega t) \hat{x} + E_0 \sin(kz-\omega t) \hat{y}$$ In my course, the Intensity of EM radiation is defined as $I = |U|^2$. ...
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Stationary Nodes with Waves containing a "Fourier series" of frequencies

For a standing wave (i.e. a wave pattern created from two oppositely-traveling waves with the same amplitude and frequency), stationary nodes are created at certain positions along the wave with ...
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Propagatuon of standing wave

We know wave is just a transmission of energy. In case of mechanical wave, this transmission of energy requires a medium so that the particles of medium can help in transfer of energy. Let us think of ...

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