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### Waves velocity for a standing wave of a string

I have done a laboratory experience to determine the speed of propagation of a wave in a vibrating magnetic string. To calculate the frequency (f) of oscillation I used an oscilloscope that calculated ...
57 views

### How fast will air travel to fill a vacuum?

Suppose I have a sealed glass cylindrical vessel of radius r and length l that is evacuated. I smash one end. How long will it take for air to (a) reach the end of the cylinder (b) fill the vacuum ...
93 views

### Problem in finding the velocity of a wave

In my textbook, the equation for a wave is described as : $y = A \sin{\frac{2\pi}{\lambda}(vt-x)}$ Now in this equation $x$ is variable as well as $y$. So when we will differentiate the equation by ...
51 views

### If 2 spaceships approaches each other at 0.99c, how much blue shift would they see? [closed]

Imagine these 2 spaceships moving at 0.99c toward each other and speed isn't additive how much blue shift would they see? I know how to calculate when the scenario is spaceship vs Earth but how about ...
56 views

### What is the interpretation of speed of a travelling wave, based on $\frac {\partial x}{\partial t}$ formula

Motion satisfies the wave equation if the following holds true $$\nu^2 * \frac {\partial ^2 \psi} {\partial x^2} = \frac {\partial ^2\psi} {\partial t^2}$$ where $\psi$ is the vertical displacement ...
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### When is the group velocity of a wave packet the velocity of energy flow?

In particular, I'm asking this for anisotropic media
815 views

### The relation between speed and wavelength

I was taught categorically that the velocity of a wave depends only on the medium in which it travels. Now I just stumbled upon a sentence + formula that declares that "the velocity of sinus-waves ...
102 views

### Intuition behind group velocity

Why is the group velocity of the wave given as $\frac {\partial w }{\partial k}$? I understand what the group velocity means but its always given as a definition and I would like to have some ...
191 views

### How come group and phase velocity can be different in a non-dispersive media?

I'm a (ex-)physicist working in the applied-physics world and was digging into group vs phase velocities. There is one thing that confuses me : when would that be the case where group and phase ...
201 views

### Sound tavels faster where?

We know that sound travels faster in a water than air. Also water is denser than air. So sound travels faster in a denser medium. But we know that sound travels faster in a warmer air and warmer air ...
214 views

### Understanding group velocity

Group velocity as a concept in Classical Waves confuse me. It's very easy to point out visually, like in this really helpful graphic here. Okay, it's the speed of the moving bulge, which, notably ...
7k views

### Are these definitions for transverse wave velocity on a string consistent?

I've found two definitions for the velocity of a transverse wave on a stretched string: \begin{align} v & = \frac{\omega}{k} \tag{1} \\[10px] v & = \sqrt{\frac{T}{u}} \tag{2} \end{align} ...
80 views

### A wave on a vertical rope [duplicate]

I'm taking a physic class and there is a problem that I'm not sure how to answer. It goes as follow: a heavy rope is tied to the ceiling. Someone jerk the rope. How will the speed, the wavelength and ...
4k views

### Is it possible to estimate the speed of a passing vehicle using a musical ear and the doppler effect?

I've found a number of questions that concern the Doppler effect, but none that seem to address my question. I have a background in music. People with a musical ear can generally tell the ratio ...
521 views

### Velocity of a Mechanical Wave on a String

I recently read a derivation for an equation which governs how quickly a wave is transmitted along a string, $v = \sqrt{\frac{T}{\mu}}$, where T is the tension in the string, and $\mu$ is the mass ...
102 views

### What is the speed of sound in a rigid body?

A rigid body has particles which never move. So will no sound travel through it ?
300 views

### Does the velocity of water waves increase with the kinetic energy of an object dropped to create them?

I'm doing a experiment that revolves around dropping an object into a container with water. When I increase the mass of the object, will the velocity of water waves increase when the object is ...
109 views

### $\omega(k)$ and $k(\omega)$ about waves

Wave propagation is characterized by the wavenumber $k$ and the angular frequency $\omega$. Sometimes (like in this answer) the relation $\omega (k)$ is preferred; sometimes instead $k ( \omega)$ is ...
443 views

### Group velocity with gaussian pulse

A gaussian pulse wave propagating in a non-dispersive medium with velocity $v$ can be expressed as $$h(z,t) = e^{-a(t - z / v)^2}$$ as suggested in this answer. In the case of a dispersive medium ...
137 views

### 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: ...
173 views

### Christmas Question

Is it still christmas day? I just lit the christmas pudding. For those unfamiliar with this tradition, one pours alcohol of sufficient concentration over the pudding and makes a bit of fuss around ...
118 views

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### If wave speed is dependent on medium only, then how to reconcile $v\propto f$?

I have read and learnt in many places that velocity of a wave depends only on the medium through which it travels. It is clear from this that the velocity of a wave doesn't depend on the frequency of ...
171 views

### Does there exist a hyperbolic relationship between frequency $\omega$ and wavenumber $k$?

As the title states, is it possible to derive a hyperbolic relationship in the form of $\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1$ between frequency $\omega$ and wavenumber $k$ I have tried to start this ...
12k views

### Why frequency is inversely proportional to time-period?

Why frequency is inversely proportional to time-period? While studying about Fourier transform that shows frequency representation. A doubt that came to me was a set of signal with same wavelength but ...
585 views

### What is the physical explanation for the phase relationship between acoustic pressure and particle velocity in plane and spherical waves?

I've been looking around for a decent physical explanation of the differences in the phase relationships between acoustic pressure and particle velocity in different types of waves. Mathematical ...
820 views

### Wave Packets, Group velocity, and Phase velocity [duplicate]

Mathematically, you find that the wave function of a particle $\Psi (x,t)$ moves with the same velocity as the velocity of the particle ($v_{particle} = v_{group}$). Is there a reason why the ...
766 views

### Displacement of an object due to opposite and equal forces acting at different times?

This question is about mechanical waves in solids, the speed at which forces propagate through solids, and the displacement that might occur due to unequal starting times of equally sized forces. ...
3k views

### What determines the speed of waves in water?

While I was walking my dog this morning, I passed over a canal filled with boats, barges, and kayaks all of different masses and moving at different speeds. I noticed that all of these vessels left ...
3k views

### Deriving the group velocity of a wave produced by some basic cosine waves with unequal amplitudes

Consider some basic cosine waves of the form ${E_i} = {E_0}\cos ({\omega _i}t - {k_i}z)$ with different amplitudes, frequencies and phases. We know a combination of such waves could result in a wave ...
560 views

### Isn't the front edge of a wave, kind of “information” which travels faster than light?

Considering the definition of phase and group velocities, We know group velocity can't exceed C but phase velocity can be infinitely high. Assume a monochromatic electromagnetic wave traveling with a ...
6k views

### What does the velocity of a wave mean?

I know that the velocity of a wave is given by $v=\lambda f$ but what does this velocity represent in the physical sense. For instance, if I am told a car moves at a velocity of 5 $m/s$ I know that ...
With the form $y(x,t)=A\sin(kx-\omega t+\phi_0)$, there are two variables, How do I find the velocity? I don't know I can apply derivative with two variables.