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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Water waves transverse

When waves arise from a point in water, they form circles around the point and it is referred to as a transverse wave. Is this because the x and y components are trigonometric graphs and so a graph of ...
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For two strings tied together: Why does a sinusoidal incident wave give rise to sinusoidal reflected and transmitted waves? [duplicate]

I am reading Griffiths' Intro to Electrodynamics (Section 9.1.3 Boundary Conditions: Reflection and Transmission) where he analyzes the case of an incident wave sent down a string that is tied to ...
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General solution of wave equation in homogenous, isotropic, linear, source-free material

Starting with Maxwell's equations we have $$ \nabla \times \vec{E} = - \partial_t \vec{B}$$ $$ \nabla \times \vec{H} = \vec{J} + \partial_t \vec{D}$$ $$ \nabla \cdot \vec{D} = \rho$$ $$ \nabla \cdot \...
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Calculating Zernike Polynomials from Image not Wavefront

Zernike Polynomials can be fitted to measured wavefronts to characterise the optical aberrations present in an image which can be corrected using adaptive optics such as a deformable mirror. For some ...
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Sound conduction in a stethoscope

i am trying to build a stethoscope and since i have no idea about physics and acoustics i wanted to ask some questions, hoping Somebody can help me. I mainly have some questions regarding the tubing ...
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Photons in communications theory

In engineering communications theory we switch between time and frequency domain interpretations. If a pulse centered at frequency F is shot out of a transmitter, it's limited time duration implies ...
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Is specific rotation a constant? [closed]

This is the formula for Specific Rotation of a solution. Can I rearrange to make c as the subject and then say that theta is proportional to c? If not, is there any other way in which I could relate ...
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If we perform fourier transform to a pure sine wave, why it gives a bunch of frequencies?

If you perform a fourier transform to a pure wave say 5 cycle per second you would get the dominant frequency of the wave it is made of. But not only it gives up the only frequency the wave has been ...
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On the definition of ray (optics) and wavefront of light

Wikipedia defines a ray as "[...] a curve that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow". But the usual meaning of a ray in ...
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If two mechanical waves interfere with each other, what is the frequency of the new wave?

Like in the title, if two mechanical waves interfere, for example sound waves with different frequencies, what is the frequency of the new wave? I know that for the beats, the frequency of the new ...
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Nodes in the air column are not always acting as nodes?

There are many representations of a standing wave column in lets say open-open instrument like flute. In this case one node centrally, and 2 anti-nodes at the openings. However, nowhere do they ...
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Maxwell equation in material media assuming periodic fields

In article https://aip.scitation.org/doi/10.1063/1.440709 authors use the following equation for treatment of electromagnetic waves in dielectric material with inhomogenous electric permitivity: $$(\...
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Can the wavelength of the standing wave be different from the wavelength of the sound it emits?

I have a question about standing waves on strings. I'll try to explain the best I can, I searched and researched the whole day yesterday but I am confused still: Every frequency has a single, and ...
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Wave nature of light [duplicate]

In a light source (like filament of bulb) there are various atoms and as such the things are deemed to be randomised. So there must be a phase difference between each of the wavetrains emitted by the ...
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Does the field vector rotate clockwise for right circular polarization when viewed from behind the source of the wave?

Descriptions and images of right or left circular polarization do differ based on a viewpoint being either behind or in front of the wave source. Furthermore, I see pictorial representations that do ...
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What are all the quantum equations to find the wave equation? [duplicate]

What are all the quantum equations relativistic and non-relativistic to find the wave equation? Is it possible to write the name of each equation and its formula, and if it is possible to explain it? ...
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How can we derive the four-wavevector from first principles?

Context From [1], I understand that, "The four-wavevector is a wave four-vector that is defined, in Minkowski coordinates, as $$\mathbf{K}^\mu = \left(\frac{\omega}{c}, \mathbf{k}\right).\tag{1}"$...
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A pulse versus a full cycle of a pressure wave

I was looking at this question, which contains this animation. It is my impression that the upper part of the animation is not consistent with the lower part. In the upper part we see that a piston is ...
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Is there an intuitive explanation as to why the de Broglie wavelength is inversely proportional to the particle's momentum? [duplicate]

Is there an intuitive explanation as to why the de Broglie wavelength of a particle (say a photon) is inversely proportional to its momentum? It can be shown, mathematically, that: $$E = h\dfrac{c}{\...
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Ultrasonic pulse-velocity measurement observation

When measuring 80cm thick concrete slab with pulse velocity technique (~22kHz transducers), we get about 210us transmission time - 3,800 m/s, which is in good agreement with expected P-wave velocity. ...
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Could a pure-transverse acoustical-waves propagate?

This is the Wikipedia definition of acoustic waves: Acoustic waves are a type of energy propagation through a medium by means of adiabatic compression and decompression Rayleigh surface waves (solid-...
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Do longitudinal waves travel faster when their origin is on the day side of the planet and destination on the night side of the planet?

1 ----> Do longitudinal waves travel faster when their origin is on the day side of the planet and destination on the night side of the planet? 2 ----> Do longitudinal waves travel faster ...
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Speed of sound in thin rods vs infinite solids

This is a followup to this answer, which states that there are two different sound velocities in a solid depending on the geometry: For 3-dimensional, infinite solids, in which the boundaries are ...
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What would happen when two wave functions intersect in a Fourier series representation of periodic signals? [closed]

I saw a piece of code on github which transforms the planetary movement into the fourier wave function. These circles are given by the x and y ordinates: x=cos(ωt) y=sin(ωt), which are periodic. ...
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Induced charge density on perfect conductor

Assuming there is a perfect conductor at $x=0$ in $\mathbb{R}^3$ and a plane EM wave $\vec{E}_i(\vec{x},t)=\vec{E_i^0}e^{i(kx-\omega t)}$ is coming from $x=- \infty$. We know, that the wave $\vec{E_r}(...
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Deriving the wave equation of a variable cross-section rod subjected to non-uniform pressure

On page $519$ of the book Engineering Vibration (which can be downloaded from here), the following wave equation of a variable cross-section rod is derived: $${ {\partial}\over{\partial}x} \Big( EA(x){...
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The phase velocity of a massive field is greater than $c$ [duplicate]

Assuming $c=1$, $v=\frac{\omega}{k}=\frac{\sqrt{k^2+m^2}}{k}>1$, for $m \neq 0$. Why is it not an issue that this $v$ is greater than the speed of light?
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Acoustic resonance inside an enclosed sphere

I apologize if this question is too basic. Assume an acoustic source suspended at the center of a hollow spherical shell. (The reason why the central acoustic source is suspended inside the sphere can ...
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Phase difference at a point due to the geometrical path difference and phase difference at source

I think the picture explains the problem I have pretty well. Basically I want find the net phase difference between rays AP and BP at P. A and B are point sources. B leads by phase difference of y at ...
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The colour of a complex light wave? [duplicate]

https://physics.stackexchange.com/q/259208 First of, as is discussed in the above question, light waves can be superimpositions of various sinusoidal waves.... Now i am no physicist, but as far as i ...
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How is the coherence of a light affected after passing through a color filter?

Basically what the question says. I want to understand it for both, temporal and spatial coherence, and also in the case of non-coherent light i.e. if the coherence changes after it passes through a ...
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Link between resonant states (quasinormal modes) in 1D wave equation, and roots in reflection coefficient?

For a simple Fabry-Perot cavity formed by a dielectric slab, the quasi-normal mode frequencies (i.e. $\omega=i \frac{c}{2nL}\ln{r^2}$, where $nL$ is the optical path difference between ends of the ...
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Finding the initial conditions of a conservation law hyperbolic system? [closed]

Consider $u(\boldsymbol{x},t)$ to be a function that is known at $t=0 $ by the initial conditions $$u(\boldsymbol{x},0)= f(\boldsymbol{x}),\quad u_t(\boldsymbol{x},0)= g(\boldsymbol{x})$$ Where $\...
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What does it imply when we say that the waves are perfectly correlated?

I am having a hard time understanding difference between correlation and coherence. I got a nice answer for coherence here- Are two waves being in phase is the same as saying that the two waves are ...
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Does resonance still occur at half, a quarter, etc. of the resonant frequency?

Examples of resonance that I have seen are pushing a swing and shattering a glass. I know the swing analogy, that if you push at the right frequency, you can make the swing go higher and higher. My ...
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Slit Experiment in a swimming pool

Would like to perform double slit experiment in swimming pool. Create waves by dropping pebbles in increasing size up to an actual golf ball. Waves travel to and through aluminum double slit screen. ...
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Contradiction in EMR theory and Planck's theory [duplicate]

In my Physics book, it's stated that Energy of an electromagnetic wave is directly proportional to intensity and it is independent of its frequency. However, Max Planck in his quantum theory said ...
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How can em waves be continuous?

Suppose we have a charge that is undergoing simple harmonic motion (an oscillating motion). Since it is an accelerating motion too, the charge radiates em waves. But here's the interesting part :- ...
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Shoaling of non-linear tsunami

Green's law predicts amplification of long waves when their amplitude is small compared to the depth. IIRC, this value is 1/20 depth. But what about after this point? What equation gives the height of ...
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Is it possible to calculate how a wind instrument will sound just based on its geometry?

It seems like it could be done like a cellular automaton, if I enclosed a very-fine 3-d grid within a surface and use cube-cell rules to define how the particles will bounce and propagate the wave ...
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Polaritons and waves

The disperison relation of a wave in general should represent the relation between its wavevector and time frequecy. For example, the dispersion relation for EM waves in vacuum is just $\omega=c\|\vec{...
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Frequency of vibration of a spring

Hi, actually I'm confused about the velocity formula (In blue boundary) why the velocity of that small element taken in that way.
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Does a wave effect remain in spacetime at the quantum level?

In Bohr's atomic model, the circumference of an electron orbit is always positive integral of the electron's wavelength. Here is an image: The circumference of an electron's orbit is always a ...
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Meaning to the wave equation solution

Mathematically, every $\mathcal C^2$ function given by: \begin{equation}c^2\nabla^2F=\dfrac{\partial^2 F}{\partial t^2}\end{equation} Can be decomposed into two other $\mathcal C^2$ functions $g,h$ in ...
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What is the function of air cavity in drums?

I'm trying to understand the function of the air cavity inside drums. I've read that 'The air cavity inside the drum will have a set of resonance frequencies determined by its shape and size. This ...
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Choosing a Complex Trial Solution for a Forced Vibration Problem and Expressing The Driving Force in Complex Terms

When solving forced vibration problems I would always choose a trial solution for the particular (stead-state) case in the form $x(t) = A \cos{\omega t} + B \sin{\omega t} $, but reading some books I ...
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What is the wavelength of red light in vacuum?

According to Wikipedia, It has a dominant wavelength of approximately 625–740 nanometres. However, I'm not sure in which medium this wavelength was measured. Was this wavelength measured in a vacuum?...
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What is not inverted when a string wave reflects with phase reversal?

When a wave reaches a boundary and it is reflected, it may happen that, if certain conditions are fulfilled, there is a phase reversal (180$^\circ$), so that what came as a crest becomes a trough and ...
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2 votes
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Interference or diffraction? [duplicate]

Suppose I have $N$ slits separated by a distance $a$. We are sending a light source of wavelength comparable to the slit width. Then which of the effect should dominate: Interference or diffraction? ...
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Misinterpretation of Louis de Broglie hypothesis [closed]

De Broglie hypothesis says that a particle also has wave like properties and gives a relation for calculating its wavelength. I have following doubts regarding it:- wave is defined as the propagation ...
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