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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Helmholtz acoustic resonance
If we take a disk of mass $m$ and area $A$ and place it in the middle a pipe of length $L$ and section $A$ containg a fluid at pressure $P$ and temperature $T$ and closed from its two ends, the disk ...
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How is energy distributed over the normal modes?
Consider a linear chain of $N$ point masses $m$ connected by linear springs $k$ and fixed at the two ends by rigid walls separated by a distance $L=N\times l$.
If I take the point mass at the center $...
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What does it mean to a have finite number of distinct physical states?
Recently I was following up on an old post of mine, about the quantization of energy. I found it had been redirected to another post asking about wavelengths. And on it I saw this remark:
"Any ...
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Using superposition in coherent and non-coherent waves to find intensity
Lets say you have 2 waves that are coherent and in-phase. Both start side by side but travel towards a point A closer to wave 1. The initial intensities will be different according to I = P/A, because ...
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Is sound really adiabatic because it is a fast process?
In many books I have consumed so far there is the statement that sound is adiabatic because heat transfer does not have nearly enough time to reach isothermal equilibrium. Doesn't this contradict ...
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The physics behind the circle / spiral of fifths
In music theory, there is this thing called the circle of fifths.
If you take a string, and you divide it in two equal parts, you get a so called octave. It is, to our ear, kind of "the same tone&...
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How are neutral conductors neutral even though they microscopically aren't?
When dealing with electromagnetic waves inside conductors we take $$\nabla \cdot E = 0$$
and I believe we use the fact that conductors are neutral to do this. However, even though conductors on ...
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Aliasing in Pulse Wave Doppler/Radar
There are many pictures on the Internet showing sampling of the output wave and then showing the phenomenon of aliasing, e.g.:
But on the other hand, I find information that in the pulse (Pulse Wave ...
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Minimum intensity fringes are not perfectly dark in diffraction pattern?
I am studying Interference and Diffraction and everywhere I look it is written that "In an interference pattern,the minima are usually perfectly dark while in a diffraction pattern they are not ...
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Can human ear hear 4 Hz frequency, if I tap my hand 4 times per second on table?
Frequency means the number of repetitions per second. Humans can hear between 20 Hz and 20 kHz, but I have a very basic question: if I tap my hand four times on a table per second, it means I am ...
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Does sound need an odd number of spatial dimensions?
In the book "when Einstein walked with Gödel" the author talks about Edwin A. Abotts "Flatland" stating that one problem which was unattended by Abott is the problem of acoustics ...
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Physical model described by modify Helmholtz equation
The wave equation $\partial_t^2u=c\Delta u$ is usually handled through a time-harmonic ansatz, which reduces it to Helmholtz equation $\Delta u+\omega^2u=0$.
I'm interested in the following modified ...
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Working Backwards from Pressure Field to Transducer
I am considering the problem of a pressure field generated by acoustic waves. If I know the specific pressure field which I wish to generate, is it possible to work back to a transducer (or array of ...
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Working principle of Shack-Hartmann Wavefront Sensor
(Image source: https://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=5287)
In the Shack-Hartmann wavefront sensor, the local slope of the incident beam's wavefront is measured as a displacement of ...
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Schrodinger's derivation of point particle motion from waves
On p. 30 of Schrodinger's Collected Papers on Wave Mechanics (1928, 2nd ed) he is deriving the equations of motion for a point particle under the assumption that Hamilton's principle function $W$ ...
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Why temporal and spatial term is multiplied to get the wave equation?
When deriving the wave equation we have:
$$y_{spatial} = A\exp(ikx)$$
$$y_{temporal} = A\exp(-i\omega t).$$
Then the overall wave equation is obtained by multiplying both time and spatial component. ...
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Types of Mechanical Waves
When knocking on a door, does that create a transverse wave or a longitudinal wave? I know it's one of these mechanical waves, but which one?
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- The minimum distance at which a radar can detect a target is 270 m. Determine the wavelength at which the radar operates if it emits pulses, [closed]
The minimum distance at which the radar can detect a target is 270 m. Determine the length of the waves at which the radar operates if it emits pulses, each of which contains 6,000 electromagnetic ...
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Is sound essentially motion?
From my understanding, the only way for humans to create sound is by moving our bodies, vocal cords, or by moving other objects. So depending on how fast we or other objects can move, different ...
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How is symmetry boundary condition related to reflection of a plane wave from a rigid flat surface?
My question is in in the context of "method of images" when applied to an incoming incident acoustic pr plane wave.
For a flat rigid surface in $XY$ system, the surface (positioned at $Y=0$) ...
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If you are on the moon, would you be able to hear your hands clapping if you're not wearing your spacesuits?
As I understand it, sound needs a medium to travel and more often than not, the medium is the atmosphere, however sound can also travel through solid objects.
And even we can hear our own voice ...
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Could the double slit experiment demonstrate not that particles behave like waves, but that together particles behave as a wave? [closed]
Clearly particles individually pass through slits, be it a single or a double slit experiment. The fact that wave interference is evident in their trajectory may be due to their interaction upon ...
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How can I find if it is gold or lead with waves? [closed]
I would find if a bowl is made of lead or gold know freqencies $w_{1}$ and $w_{2}$ and a vibrator induces waves at $z=0$ (and there are reflected waves). I do it with progressive plane electromagnetic ...
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Can a standing wave indistinguishable from a travelling wave for a stationary observer?
Say that you place an observer at a point in space where the non-zero amplitude of a standing soundwave is equal to the amplitude of some travelling soundwave (that is, the two opposing travelling ...
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Is it not possible for true standing waves to appear in nature?
From what I understand, standing waves form when the following conditions are met: 2 waves of equal frequency, amplitude, and polarization are travelling in opposite directions. So if any of those ...
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Difference between structural acoustics and flow induced acoustics
I'm researching about sound induced inside water pipe and came up with some questions. For numerical acoustic calculation, I found two ways.
Using acoustic analogy such as Lighthill equation or ...
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Phase Angle: AC Circuit
I am seeing this everywhere when I look up impedance and reactance for AC circuits. Below is a picture below from the website here.
They say the formula for the phase angle is $y=\sin(\omega t+\phi)$....
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Paraxial Spherical wave emanating from point source
I'm reading through chapter 5.3.1(Impulse response of a Positive lens), in Goodman's "Fourier Optics"(p.109). An object is placed a distance $z_1$ in front of a lens.
If we place a point ...
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Two-Ray Ground-Reflection Model: Understanding the Difference in Phase Offsets at the Receiver
Currently, I'm trying to understand the Two-Ray Ground-Reflection Model.
During my research, I came across the following simplification expressing the received power as follows (taken from Wikipedia):
...
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Is the argument of the $\sin$ function for a monochromatic plane wave dimensionless?
I was looking at the following representation of a monochromatic plane wave:
$$
F(\vec x, t) = A\sin(2\pi\nu(\vec x \cdot \hat n - ct) + \phi)
$$
but, upon analyzing the argument of the sin function, ...
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On sum of amplitudes in Wave Mechanics
Consider Schroedinger equation, which I write in the form $$ (\mathscr{L}+V)\psi=0$$where $\mathscr{L}$ is the kinetic and time-derivative operator. Now, imagine I have two point sources 1,2 with ...
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How do the forces involved in EMR continue to occilate past emmision of a photon
If electric fields are created by an accelerated charged particle, such as an electron, and magnetic fields are generated by electric fields in motion, what are the individual fields that make up ...
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What is the relevant phenomenon behind Undulatus/Radiatus cloud formations?
I am seeing many people claiming that cumulus clouds that sometimes form periodic wavy patterns (see images for "altocumulus undulatus" or "Radiatus" for instance) have no ...
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What is an electromagnetic wave exactly?
This question might be very silly, but I am really confused about it from several days.
Look transverse waves on a string propagate along the string due to the electromagnetic (EM) forces between ...
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Why the consecutive spherical wavefronts produced by a rest point source are not equidistant? [closed]
I learnt that a point source produces spherical wavefronts and i know the reasoning behind that too and while studying the concept again a question popped in my mind, that "Are those spherical ...
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Can two normal 1D waves form a wave packet?
I have a confusion
A wave packet is described by the superposition of two wave functions: $$Ψ_1(x,t)=A\sin(k_1x−ω_1t)$$ and $$Ψ_2(x,t)=A\sin(k_2x−ω_2t),$$ where $k_1=2.0×10^6\text{m}^{−1}$, $k_2=3.0×...
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Is there a Doppler effect on the surface of an expanding balloon?
Imagine a stationary transmitter which vibrates the surface of the balloon and a stationary receiver half way around the balloon that can pick up these waves. Let the balloon expand. Will the ...
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Does a linearly accelerating spherically symmetric body emit gravitational waves
According to Birkhoff's Theorem, any spherically symmetric body will not emit gravitational waves. I can understand this for an object that is contracting and expanding because from far away the ...
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Why does the formula that I provide derivation for contradict the de Broglie equation? [duplicate]
I'm trying to come up with a formula relating the wavelength of the electron and the potential difference that it was accelerated by. My derivation goes like this:
Let's say the electron is ...
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Bloch Wave Solution to the Oscillating String
I am taking a graduate-level mechanics course right now, and we are working with the continuous limit of coupled harmonic oscillators. My professor mentioned that he prefers the "bloch wave ...
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How do you interpret the statement that a wave is a travelling wave if $f(x,t) = f(x \pm vt)$?
I came across the statement that a wave is a travelling wave if a wavefunction $f(x,t)$ can be written as
$$
f(x,t) = f(x \pm vt)
$$
but this doesn't really make any mathematical sense to me. How can ...
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Acoustic wave incident to pipe wall
I would like to consider the sound incident to a water filled pipe wall. I think the pipe wall is typically considered as a rigid wall boundary, it means all the incident wave is reflected.
Is this ...
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How do you calculate phase from sin wave equation?
So if a wave equation is $A \sin \left(k x - \omega t + \phi \right)$ then how can you calculate what the phase would be? From the graph, it is visible to see where the graph has shifted but just by ...
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How can acoustic velocity of plane wave be derived using acoustic pressure?
I am going though the section on plane travelling waves from the book by G.D.Pierce,"Acoustics: An Introduction to Physical Principles and Applications". I am unfortunately stuck at a place ...
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Refraction of light - Huygens' Principle
To elucidate the rationale behind the bending of light as it transitions between different mediums, Huygens' principle is predominantly employed. The procedure, as demonstrated in this video (link: ...
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Why do we only consider tension pointing toward one direction when deriving the power of wave on a wire?
How about the tension pointing in the opposite direction? Does it not contribute to the work done by wave to make the wire move up and down too?
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Simple Harmonic wave-Particle velocity for a snapshot:
Is my diagram correct(vp corresponds to particle velocity). Wave equation: y=Asin(wt-kx)
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How do you represent a plane wave propagating at an angle $\theta$ w.r.t. $z$-axis? [closed]
There is a plane wave $\exp(i\mathbf{k}\cdot\mathbf{r}-i\omega t)$, where $\mathbf{k}$ is the wave vector. Suppose this wave propagates at an angle $\theta$ w.r.t. $z$-axis. What will be the wave ...
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Work Done by Buoy When Displaced by Wave
I have a cylindrical buoy with the flat parts on top and bottom respectively. The radius of the buoy is 3 mts. It's hit by a wave with an amplitude of 1.5 mts and a period of 7.3 sec. I want to know ...
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Conceptually, what does the amplitude term in the wave equation represent when describing a gravitational wave?
I'm trying to conceptually understand what the amplitude term in the wave equation for a gravitational term represents, which is depicted as $A = A_0\cos(\omega t-kx)$ where $A_0$ is the amplitude ...
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