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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Michelson interferometer: beam splitter affects amplituedes?
Let's suppose an initial plane wave $\vec{E}=\vec{E_0}e^{i(\vec{k}\cdot\vec{r}-\omega t)}$ enters a Michelson interferometer . Let $\vec{E_1}=\vec{E_{01}}e^{i(kz-\omega t)}$ and $\vec{E_2}=\vec{E_{02}}...
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Intensity of light and energy at a photonic level
If I understand correctly, the intensity of light is proportional to the number of photons hitting a certain area.
If we then look at a single photon when described as a transverse wave, is its own ...
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Controlled oscillation of a piano string by electromagnetic, mechanical, or other means [closed]
What would be a good way to actively control the loudness of an acoustic piano note over time after the note has already been struck by the hammer, such as by actively changing the amplitude of a ...
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How does the Resonant Frequency of a Tibetan Singing Bowl change according to the depth, viscosity and temperature of the liquid inside it [closed]
I'm doing my Physics Extended Essay for IBDP related to the variations of frequency in a Tibetan singing bowl with respect to depth, viscosity and temperature of liquid. While i can model the ...
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What is the relationship between contact area in a collision and the volume of sound produced?
Greater contact area produces a greater sound in a collision, but why does that happen, and what is the proportionality?
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Beat frequency and phase difference
Equation for mechanical wave:
$$ y = A \sin \left( k x \pm \omega t \right) \tag{1} \label{1} $$
Here, $k = \frac{2 \pi}{\lambda}$, where $\lambda$ is the wavelength and $\omega = 2 \pi f$, the ...
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Is the intensity of any type of wave proportional to the amplitude squared?
Assume that a wave is any function of a physical quantity $y$ that respects the equation:
$$\nabla^2y=\frac{1}{v^2}\frac{\partial^{2} y}{{\partial t}^2}.$$
Is there any way you can prove that the ...
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Is it possible to make large waves from perfectly timed single drops of water?
Assume I have a hemispherical container of water and an eyedropper. Is it possible to add water to the container one drop at a time, such that each drop continues to add kinetic energy to the water?
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Poisson spot amplitude
The equation
$$
U(P) \propto \int_0^{2\pi} \int_0^{\infty} g(\rho,\theta) \exp\left[ \frac{i\pi}{\lambda}\left(\frac{1}{z_0} + \frac{1}{z_1}\right) \rho^2 \right] \rho \, d\rho \, d\theta
$$
or the ...
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Poynting vector and plane waves
Suppose the electromagnetic field at a point is a superposition to two plane waves $(\vec E_1, \vec H_1)$ and $(\vec E_2, \vec H_2)$. If the two plane-waves have different frequencies, the (time-...
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Why does a higher frequency mechanical wave have more energy?
(that question may sound like my last question What makes a higher frequency sound wave more energetic? but I wouldn't consider it a duplicate, the focus is very different.)
Comparing two mechanical ...
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What makes a higher frequency sound wave more energetic?
The energy of a mechanical wave (in this case, the sound wave, which stimulates periodic movements of a gas) is proportional to both amplitude and frequency. Often, I read that it is written that ...
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Lorentz Transformation of Wave Equation
Consider a 1D Wave equation: $$\frac{\partial^2 y}{\partial t^2}=v_1^2\frac{\partial^2 y}{\partial x^2}$$ So, we are given two frames, S and S' (moving along $x$-axis) with velocity $V$ relative to S. ...
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Why do parabolic antennas need to be the same width as their wavelength?
I am reading the wikipedia page for parabolic antennas, and have a question about the below quote:
In order to achieve narrow beamwidths, the parabolic reflector must be much larger than the ...
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Equation of a reflected electromagnetic wave
According to my textbook, for an electromagnetic wave travelling to the left:
$$ E = E_0 \cdot \cos(kx - \omega t) $$ and $$ B = -B_0 \cdot \cos(kx - \omega t) $$ where E is in the y-direction and B ...
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Nearly Free Electron Model (Perturbation Theory)
I am having difficulty understanding the degenerate perturbation theory treatment of the nearly free electron model. So for a free electron, the energy dispersion is relation is $E^{0}=\frac{h^{2}k^{2}...
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Physics model for my tub of water demo
I want to setup a demo to show people an intuitive example of causal inference (Pearl 2009) using a simple experiment.
I have a tub of water with two accelerometers floating on the surface. In the ...
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Why is my phase difference so off? [closed]
I've got two sine waves whose arguments differ only by a phase difference I'm calling phi. I'm trying to reverse engineer this phi from the sine waves I've created.
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Mechanical wave traveling time in a medium
This stems out of my personal curiosity and it's not related to any homework of sort.
Suppose I have a table made of some uniform substance (like plastic), and then I strike some point of the table ...
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What are the exact conditions for the constancy of the speed of a wave?
Do two mechanical transverse waves traveling in the same medium have the same speed whatever the source might be? If the answer to this question is yes, can I generalize and say "all waves of the ...
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I need a must-have reference or handbook about the numerical solution of the 3D wave equation
I'm looking for an encyclopaedic book on numerical simulation of the 3D wave equation.
One that is a must-have reference with finite differences, finite element and spectral methods.
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How does loudness decrease with distance? [duplicate]
Let's say there's a speaker in a huge open space on the Earth's surface. The speaker blares a sine wave with frequency $f$ Hz and and volume $V_0$ decibels.
How does the volume (in decibels) decrease ...
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Terminology: angular frequency vs frequency
I am confused about the usage of the terms frequency and angular frequency in physics texts. E.g. in the book "Classical Electrodynamics" of J.D. Jackson, one considers in formula (7.3) page ...
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How to understand the derivatives in wave equation?
I am looking at the derivation of the wave equation, but I am stuck on the math. Specifically, in the following:
How do they get the equivalence between $\frac{\partial}{\partial z} (\frac{dg}{du}) = ...
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How does sound travel in the form of transverse wave in solids and on the surface of liquids?
I am not able to comprehend. Can someone explain by visualizing that how it happens ?
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Learning about diffraction of waves
I'm a math major learning some physics for a QM class. I am looking for some sources to learn about diffraction of waves.
Online, I've found some treatments on YouTube and other sites, but these seem ...
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Electron as a wave function, is it a wave bubble? [closed]
Something I have been pondering.
We tend to think of a physical particle as a grain of sand or at atomic levels maybe an electron(lepton).
If I now choose to consider an electron as a wave, typically ...
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Can someone please explain how is the setup stated below apparently causing amplitude resonance in spite of different frequencies?
Suppose I have a pendulum such that its natural frequency is $2 Hz$.
I release it from One extreme by striking it with a tuning fork of frequency $1 Hz$. Now in $0.5s$, the pendulum will undergo 1 ...
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Inhomogeneous Solution to 2+1D wave-equation
The inhomogeneous wave equation
$$\left(\frac{1}{c^2} \partial_t^2 - \Delta\right)G(\vec{r},t)=\delta^3(\vec{r})\delta(t) \tag{0}$$
for a point-source in three spatial dimensions can be tackled by ...
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Can we say that amplitude of light scattered by air molecules is inversely proportional to the square of wavelength of incident light?
As per Rayleigh's criteria of scattering of light by air molecules the intensity of scattered light is inversely proportional to the forth power of wavelength.
AND WE ALSO SAY :
Intensity of a wave ...
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Longitudinal wave in a falling elastic body
Consider an elastic rod hung from a high point with density $\rho$ and Young's modulus $Y$, subject to gravitational acceleration $g$. The coordinate from the hanging point is $x$, while the ...
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Doubt about superposition principle [closed]
The superposition position in waves is defined as 'the total displacement produced equals vector sum of individual waves.Given that 2 sources S1 and S2 produce waves who's displacement are y1 and y2 ...
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Suspiciously wrong value by factor of $1/2$ in experiment to calculate frequency of AC mains using sonometer
In school we performed the following experiment:
We use a step down transformer ($220V$ to $6V$) and pass current through a "sonometer wire". We have a meter scale underneath the wire. ...
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Is there a general solution for 3d Wave equation?
The general solution for 1D Wave equation is generally given as
f(kx-wt)+g(kx+wt)
Is there such general solution for the 3D Wave equation?
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Do waves need the same amplitude to be coherent?
I am wondering whether amplitude needs to be constant for two waves in order to be coherent. From my understanding, coherent waves only need a constant phase difference and frequency. Amplitude does ...
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Phase difference of standing waves
The phase difference of a standing wave is zero.
The above statement is found online when searching about standing waves. However, it doesn't make much sense to me.
Consider the above diagram of a ...
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Can mechanical waves exist in zero gravity?
Just got out of a test and there was this question asking of true/false:
“A fluid presents pressure variation only when subjected to a gravitational field”
To which the alleged correct answer was “...
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Harmonics in closed and open pipes
What exactly would happen if we sent a frequency that was not one of
the harmonics into a closed and open pipe? What would happen if we
gradually increased this frequency?
From my understanding, I ...
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How is the energy distributed over the harmonics of a standing wave? Does it follow an exponential decay law?
A string that gets plucked produces overtones or harmonics if I am not mistaken. The frequencies are given by:
$$ f_n = n \frac{nv}{2L} $$
The energy of a standing wave is given by:
$$ E_n = \mu \...
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Why does water come out of a bottle in waves?
So imagine you have a bottle of water or any type of liquid (like a bottle of milk that has just been opened)that is completely full or even three quarter of it is full,why does the water or milk come ...
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Wave equation ON a sphere
I was thinking of those videos of football players in slow motion, where they hit the ball, and a wave propagates all along it.
I know you can describe a wave in different kinds of coordinates, with:
$...
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EM waves in Anisotropic media: source of the index ellipsoid equation
I'm reading Amnon Yariv & Pochi Yeh's Photonics book, and trying to follow the derivation in section 1.7. I understood rather well the Fresnel's equation of wave normals, quoted here for ...
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Overview work on radio solitons?
I've heard about solitons in dense mediums (water), sparse mediums (acoustic) and optical fiber.
But I can't find a good overview work on solitons in radio spectrum. Something like generating EM ...
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Derivation for the interference of two plane waves
I am trying to understand the derivation for the intensity of two interfering waves. In my textbook, I see this:
I am confused by everything on the first line, namely:
It seems like we are ...
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Phase difference of antinode and node? [duplicate]
How do I determine the phase difference between particles A and C? Particles A oscillates up and down, but particles C remains unchanged. So it seems that the phase difference varies between A and C ...
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Phase difference problem
What's the phase difference between A and B on the following diagram. Where it is a standing wave. This question doesn't even make sense to me as from watching animations of standing waves, points A ...
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How can a laser be narrow?
In my understanding, light works as follows: every point in space where there is light, this light works as a point source. When we progress in time, the light spreads out from there in all directions ...
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Phase difference with standing waves
Consider the diagram above.
We say the phase difference between two particles vibrating between two consecutive nodes is zero. Hence we say that points B and E are in phase. However we say that points ...
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When the angle of incidence is equal to critical angle, which medium will the wave be considered to be in and will the wave properties change?
I am a student in 10th grade and we were discussing total internal reflection in class today. My teacher told us that when the angle of incidence is equal to the critical angle total internal ...
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What's (intuitively) the $k$ in the de Broglie formula?
Background: I'm currently doing self-study of quantum physics by following university level quantum physics lectures on YouTube (e.g. the YouTube MIT 8.04 Quantum Physics I, Spring 2013 or Stanford ...
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