Waves are disturbances that propagate throush 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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How to model the form of a surface water wave?

Normal surface water waves, as generated by wind, do not have sine form but wave peak is higher and shorter than wave trough with different wave steepness. What parameters characterize such a surface ...
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691 views

Boundary layer theory in fluids learning resources

I'm trying to understand boundary layer theory in fluids. All I've found are dimensional arguments, order of magnitude arguments, etc... What I'm looking for is more mathematically sound arguments. ...
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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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What does a de Broglie wave look like?

What does a de Broglie wave look like? Are de Broglie waves transverse or longitudinal? Can they be polarized? What about the de Broglie wave of a ground state neutral spin-zero Helium 4 atom? ...
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7
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223 views

Does a wave experiencing a total internal reflection penetrate the medium in any way?

Let me explain my concern usingn this picture: At the point of total internal reflection does a fraction of the wave get into medium 2? I would imagine it should happen because of the uncertainty ...
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383 views

Huygens wave theory not applicable to lasers or parallel beams of light?

According to Huygens wave theory, every point on a wavefront acts as a secondary source of waves. Using this principle we can never have pretty narrow parallel beams of light right? Like lasers? ...
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De Broglie wavelength, frequency and velocity - interpretation

Two fundamental equations regarding wave-particle duality are: $$ \lambda = \frac{h}{p}, \\ \nu = E/h .$$ We talk about de Broglie wavelength, is it meaningful to talk about de Broglie frequency ...
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563 views

How does infrared light 'erase' phosphorescence on zinc sulfide?

I found some sheets of zinc sulfide in my basement that phosphoresce green for up to 24 hours or so after exposure to bright light in the violet range or shorter. One of the first things I tried was ...
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412 views

Box normalization

Whenever we study free fields, the solutions of these fields (or particles, whatever feels most comfortable) are always given by plane waves. The dispersion-relation $\omega=\omega(k)$ will of course ...
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275 views

Are small speakers inherently limited to higher frequencies?

I am hoping to build a subwoofer using multiple smaller speakers (165mm) instead of a single larger speaker (380mm). My theory is that the displaced air volume is what matters, not the individual ...
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540 views

How do traveling waves pass through a standing wave node, if the node doesn't move?

I'm having trouble with the explanation that a standing wave in a string is the superposition of traveling waves. The nodes in the diagram above are points where the particles of the string's ...
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343 views

How to simulate a crashing wave? [closed]

I'd like to create a very rough animation of a wave crashing on a beach. I'm guessing it would have to be a particle simulator, where you code in the forces between the particles and then integrate ...
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123 views

Minimal Extension of Wave Equation to Include Dispersion

Let's say you are modeling some process with the wave equation $\frac{1}{c^{2}}\frac{\partial^{2}\psi}{\partial t^{2}} = \nabla^{2}\psi$. You wish to improve your model by including dispersive ...
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364 views

Will a wave packet undergo dispersion when traveling down a hanging rope?

Suppose I tie one end of a rope to my ceiling and the other end to a spot on my floor directly underneath it. Because the rope has some mass, the tension varies along the rope, from highest at the ...
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1answer
105 views

Critical bathymetric profile to maximize surge and minimize breaking?

Reading about storm surge, I found it fascinating that the gradual slope of the Gulf Coast of Florida resulted in a much higher storm surge but much lower energy release in breaking waves. Is there ...
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1answer
392 views

The role of metric in the Wave Equation

The wave equation is often written in the form $$(\partial^2_t-\Delta)u=0,$$ involving the Laplace-Beltrami operator $\Delta$. However, the Laplace-Beltrami operator $\Delta$ is defined only in the ...
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163 views

How to reproduce highway vibration?

I would like to test my hardware under vibration that can appear on a highway gantry. If someone has a model of such vibration. i.e period and amplitude. In my lab I have a motor that can be ...
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666 views

Can someone explain how water from a garden hose can propagate in a sine/cosine wave?

A video posted on Youtube. How does this phenomenon work? I know he is using frequency to propagate water in a sine/cosine wave, but how does it exactly work this way? Why do we see it as if its ...
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3answers
711 views

Why can't light penetrate solid objects?

Light is combination of perpendicular electric and magnetic fields, since electric fields penetrate a conductor, why can't light travel in them? I think my argument does sound stupid, but I can't ...
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196 views

Multiple channels of information in single electromagnetic wave?

I'm trying to understand how can multiple radio stations transmit information just by transmitting using different frequency. The way I understand it all those different frequency waves add up to a ...
6
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960 views

What is the mass of a wave?

The slide called "QUANTA" here says that "One Quantum has a definite mass" and the picture shows a wave. So, What is meant by the mass of a wave?
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449 views

Is a soundproofed wall really only as strong as its weakest area?

I've seen a few questions about sound waves and sound travel here on Physics SE, so I'm hoping this question is a good fit for this site. During my internet research on soundproofing, I've come ...
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Galilean transformation of wave equation

I have this general wave equation: \begin{equation} \dfrac{\partial^2 \psi}{\partial x^2}+\dfrac{\partial^2 \psi}{\partial y^2}-\dfrac{1}{c^2}\dfrac{\partial^2 \psi}{\partial t^2}=0 \end{equation} ...
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How to Make RF Waves Visible

I understand RF (Radio Frequency) Waves are electromagnetic waves and a mode of communication for wireless technologies, such as cordless phones, radar, ham radio, GPS, and television broadcasts. Most ...
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718 views

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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498 views

What are the normal modes of a vertical rope?

Closely related to this question on traveling waves on a hanging rope, I would also like to know what the normal modes are on a rope that hangs vertically, fixed at both ends. Tension in the rope ...
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180 views

Is it possible to estimate the speed of wind by the sound emitted by a cable of an overhead power line?

I was near ($\approx40m$) an overhead power line and I heard a sound coming from the cables of the power line; I think the sound was made by the vibrations of the power cables due to the wind but I am ...
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186 views

Is Huygen's Principle Axiomatic?

Is Huygens Principle just a fundamental way to understand light? It always seemed to me that it was somehow "derived" or that it should be-but is it simply a well-founded theory?
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356 views

What is a wave?

I was watching an outtake of Prof. Brian Cox talking to a tv producer about "gravity waves". Their discussion got a bit side-tracked, because the non-scientist didn't seem to understand what a wave ...
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3answers
328 views

Controllable faster-than-light phase velocity

This is not another question about faster-than-light travel or superluminal communication. I totally appreciate the speed limit capped by physical laws (or theories.) Just curious, since there is no ...
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1answer
510 views

What's the optimal shape for a continuous Galilean Cannon?

A Galilean Cannon is a toy similar to the famous basketball-and-tennis-ball demonstration. You take a tennis ball, balance it on top a basketball, and drop them both. The tennis ball will bounce up to ...
6
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1answer
143 views

Does a square wave “smooth out” in the air?

I understand that playing a square wave from speakers cannot produce a PERFECTLY sharp division between compression and rarefaction. But it's sharp enough to sound distinctly different from a sine ...
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1answer
71 views

Wavy stream of liquid

When pouring a liquid into a glass some streams have a wavy shape, like the one in the following photo: (Couldn't find a better picture, sorry.) What causes the stream to be of such a shape?
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215 views

How is it possible for an Ultrasound device to correctly interpret a negative density change in tissue?

I understand the principles of Ultrasound Imaging, and the mathematics behind sonar velocity, impedance, and reflection. I also understand that an Ultrasound device recieves an echo produced by ...
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Reflection of transverse and longitudinal waves

Why is it that when a transverse wave is reflected from a 'rigid' surface, it undergoes a phase change of $\pi$ radians, whereas when a longitudinal wave is reflected from a rigid surface, it does not ...
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2answers
373 views

If electrons behave as standing waves when they are bound to an atom then how do they carry charge?

Today in my physics lesson we learnt that the best way of describing the behaviour of an electron that is bound to an atom is to treat it as a standing wave. I understand that this is the ...
6
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1answer
142 views

“Book domino” propagation speed?

I was watching this video on the Guardian website. As it can be seen, the "wavefront" of the fallen books travel with a fairly constant speed, which I guess depends on the mass of the book $m$, on its ...
6
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1answer
322 views

Why does the echo for soundwaves hitting a vacuum come back out of phase? [duplicate]

Possible Duplicate: Phase shift of 180 degrees on reflection from optically denser medium I've read in a physics book for musicians that, when a soundwave hits a near-solid object, it ...
6
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1answer
197 views

The Mysterious Reverb in a Jar of Hair Gel

I have a small jar filled with hair styling gel (or, as it calls itself: Ultra Gel-Wax). The jar is cylindrical(with the height being less than the width), has an unscreweable lid and is made of ...
6
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184 views

How does one explain this pattern generated by earthquake waving driving a pendulum?

How to explain this pattern generated by earthquake wave driving a pendulum? Specially, there are three groups of curves that look categorically different: 1) The group of curves outside the ...
6
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2answers
171 views

How do the LASERs in LIGO realize that space has expanded as a gravitational wave passes by?

I read an article on LIGO, and I heard it mentioned that it is a nontrivial argument to say that the effect can be measured by interferometry. What happens to space as the wave passes? Does the light ...
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2answers
186 views

Relaxation time for deviations from spherical shape of a black hole's event horizon (and waves)

A different question about truly spherical objects in nature (Do spheres exist in nature?) made me think of a lecture I had been at where, as I recall, it was mentioned that the most perfectly ...
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What makes laminar cascade break?

Near my house there is a mall that have a cascade, which has a pratically constant flow, and doesn't seem to have perturbations (at least near the edge where water falls), between its two levels. ...
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8answers
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Doppler's effect use

While i was in high-school i learn't the Doppler's Effect which if i remember correctly is: The Apparent change in the frequency of sound caused due the relative motion between the sound and the ...
5
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4answers
782 views

Optical explanation of images of stars?

Very often when viewing pictures of the cosmos taken by telescopes, one can observe that larger/brighter stars do not appear precisely as points/circles on the image. Indeed, the brighter the light ...
5
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3answers
416 views

Physics of a guitar

I understand that when you pluck a guitar string, then a bunch of harmonic frequencies are produced rather than just the frequency of the desired note. If this is true, why does C2 sound so different ...
5
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1answer
834 views

How does a speaker produce sound?

What I read is that a speaker produces sound by the movement of a coil attached to a cone which moves back and forth. So, If I try to move the coil by hand, would it produce sound? If not, why? or Why ...
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410 views

Which solution to the electromagnetic wave equation is the most accurate model of monochromatic light?

When a photon is modeled as a monochromatic electromagnetic wave its electric and magnetic components are usually taken to be sine waves (for example here ...
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101 views

Discretizing the Wave Equation in polar coordinates

I want to discretize the wave equation $$\frac{1}{c^2}\frac{\partial^2\psi\left(\vec{r},t\right)}{\partial t^2}=\triangle\psi\left(\vec{r},t\right)$$ in polar coordinates. I find the following ...