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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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Finding frequency on vibrating string, please post solution

a string fixed at both ends os vibrating in lowest mode of vibration for which a point quarter of its length from the point is the point of maximum vibration . The node emitted has frequency 100hz. ...
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Rhythmodynamics [on hold]

I'm looking for some review or opinion about rhythmodynamics theory: http://mirit.ru/rd_2007en.htm What are weak points of this theory?
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Can inhomogeneity in the medium accelerate particles

Suppose I have a charge which is moving in through a medium with constant velocity. Now, what will happen to the charge as it encounters an inhomogeneity in density? whether it will accelerate or ...
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33 views

Global destructive Interference and conservation of energy

As an engineer I see it like this. Imagine I send a wave and then I send another wave in phase shift to cancel that wave. Unless I am sending the wave from exactly the same point in both instances, ...
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How to calculate fringe separation for a double-slit experiment? [on hold]

Given two slits a distance $2\,\mathrm{mm}$ apart and $1.33 \, \mathrm{m}$ from a screen, with a monochromatic light of frequency ${4.10}^{13} \, \mathrm{Hz} ,$ what's the value of the fringe ...
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Nasty longitudinal waves question [on hold]

Bit of a horrible waves question which neither my friends nor teachers could work out and explain. Any help would be much appreciated
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Why does a narrower Gaussian wavepacket correspond to an increased $\Delta k$?

Please answer this question without too much reference to the Uncertainty Principle. I understand it in that respect. I'm just wondering in terms of Fourier analysis. Why does a more localized wave ...
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1answer
53 views

Quantum micro canonical ensemble

In Huang's Statistical Mechanics, the quantum micro canonical ensemble is introduced in an unorthodox way. Here, the isolated system of the classical ensemble is supplemented by an external reservoir (...
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2answers
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Why does the length of a pendulum cause different natural frequencies of pendulums in Barton's pendulum?

In Barton's pendulum, the pendulum with string that is the same length, L, as the brass bob (source of driving frequency) has natural frequency equals to the bob's driving frequency. The pendulum ...
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When a bell rings continuously, the waves produced in air are : [on hold]

Options are Transverse Waves, Electromagnetic Waves, Pulses and Longitudinal Waves. I think the answer is longitudinal waves but it is given pulses
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Standing waves on a guitar

If we play different strings we get different frequencies as the densities of the strings are different. This is described by: $$kL=n\pi$$ where $n$ is an integer, $k$ the wavenumber and $L$ the ...
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2answers
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Physical reasoning behind hearing a single shock

When an object is flying in the air at a mach number ($M$) greater than 1, a shock wave is continuously produced and the mach cone makes a particular angle, $\theta_M$, with the ground (or normal). An ...
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3answers
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Wave and relativity

From Wikipedia, "In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport." But Einstein said that energy equals mass so if a wave ...
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1answer
35 views

Wave equation for a static fluid that does not flow

From the fluid dynamics, applying a linear approximation, I arrived at the following master sound-wave equation: \begin{equation} \partial_t \left( - c_S^{-2} \rho_0\left( \partial_t \psi_1 + \mathbf{...
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Estimating the maximum frequency of waves on a fixed string?

I would like to understand if/how I can estimate an upper limit on the frequency of (standing) waves that can be generated on a string fixed at both ends. As a first step, the properties of the ...
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7 views

Phase change in reflection from mirror

I know that a wave have 180 degree phase change when it goes from a rarer medium to denser medium. So does the phase change when light is reflected from mirror. Here how can we say that light ...
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K constant in 3D solution to wave equation

I'm following how it was obtained the general form of a wave equation in 3D rectangular coordinates. The solution was worked with the $E_x$ component of the electric field. It was shown how to obtain ...
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can the amount of air in a pipe be calculated by the frequency spectrum it produces?

I'm interested to know if there is a way to measure the volume of air that flows through a pipe per unit time just by listening to it. I know that ideally, I can calculate the resonance frequency from ...
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1answer
19 views

Phase Changes during Reflecion

I want to ask that whether there is any phase change during reflection of a P-polarised wave? I know that for a S- Polarised wave there is a phase change of 180° when wave travels from rarer to denser ...
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1answer
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How can $2\pi/\omega = T$, when it is equal to $\lambda/v$?

I can conceptually understand that $2π/$angular frequency will result in the period. $2π$ represents a full cycle, and $\omega$ represents the angle per second of the wave. Then, it follows that a ...
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3answers
50 views

How do sound waves from different distances not mess up the pitch?

This might be a too begginer question for this site, but, if two sounds are produced with same pitch from different places, why do they sound like the same? Why do they "sync" their vallies and peaks ...
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4answers
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Why do we use the RMS but not the fourth root mean quad?

Why do we use the power of $2$? What is the relation between this and having the same heat energy in both AC and DC?
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1answer
84 views

Shock waves at $M = 1$ and $M > 1$

When a wave moves faster than the local speed of sound ($c_s$) in a fluid, there is a shock wave since the fluid is unable to respond to the moving wave. Even if velocity ($v$) is constant, if ...
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What does it mean to make a sound twice as loud? [duplicate]

Giancoli Textbook question: To make a given sound twice as loud, how should a musician change the intensity of the sound? The given answer is: "Increase the intensity by a factor of 10." I don't ...
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Fixing the Poisson equation to match the deformation of elastic sheet with experimental observation

I am working on the calculation of the deformation of a circular elastic sheet with radius $R=1.2~m$ when a plate with mass $M$ and radius $r_0 = 4~cm$ is sitting in the center of the sheet. I used ...
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1answer
35 views

Sinewave in DC powersupply

today in our physics class we talked about the hall-effect. Therefore we have used a Lab Quest with a sensor to measured the magnetic flux induced by a coil. While adjusting the current to gather some ...
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2answers
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What is the physical interpretation of dividing $2\pi$ by a variable?

Looking at the angular wavenumber eqn: $$k = \frac{2\pi}{\lambda} = \frac{2\pi\nu}{v_p} = \frac{\omega}{v_p}$$ I'm curious what it means to divide $2\pi$ by the wavelength and why $2\pi$ was chosen....
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What would the curl of a longitudinal wave mean?

Is the curl of longitudinal waves even defined? Would the curls of a longitudinal wave and a transverse wave be different in any way?
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1answer
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Variation in Young's double slit experiment

In Young's double slit experiment two rectangular slits are used.What will happen if instead of two rectangular slits two concentric circular slits(of small radii) are used,the distance between their ...
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2answers
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Question About Relation Between Time and Color of a femtosecond Laser Pulse

This is a problem in Tipler's Modern Physics: Laser pulses of femtosecond duration can be produced, but for such brief pulses it makes no sense to speak of the pulse’s color. To demonstrate this, ...
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5answers
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If two sound waves that are different frequencies create beats that occur several hundred times per second, can you hear this effect as its own tone?

If you have multiple waves of different frequencies, the interference from the different waves cause "beats". (Animation from https://en.wikipedia.org/wiki/Group_velocity) Let's say that a green dot ...
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1answer
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Wave optics, intensity distribution

Do Gaussian beams have a gaussian intensity distribution? If so, why? Does the intensity distribution depend on the profile of the light beam?
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1answer
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Is the energy of a vibrating string the classical analog to Born's rule?

Consider this Phys.SE question which spells out the energy of a vibrating string as a variant of Hooke's law, and thereby explains why it's proportional to the square of the amplitude (here: the ...
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1answer
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What physical property can has the greatest average effect to anticipate the transmission speed of a substance?

Rubber is often regarded as having one of the slowest transmission speeds while aluminum and steel have some of the highest. Density alone can't account for this as air is less dense than rubber but ...
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1answer
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Why does acoustic imepdance increase when mass density and bulk modulus increaes?

If we take some material and (somehow) increase its mass density or bulk modulus then its acoustic impedance will increase as $z = \sqrt{\rho \kappa}$. That is, it What is the physical reasoning ...
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How can scattering attenuation eliminate flux in lossless media?

In lossless media (like elastic materials or non-conductive dielectrics) one can set up scattering problems involving inclusions of heterogeneous impedance as in Mie and Rayleigh scattering. Somehow, ...
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1answer
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How do you find the cutoff frequency of a wall of a particular depth?

You've pobably heard that low frequency sound waves almost always tend to pass through big walls while high frequencies never make it. The pattern is clearly consistent, but what is an actual formula ...
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Young's experiment

Young's experiment was conducted by Thomas Young. In his experiment, he used two coherent light sources and observed Fringe patterns. Now I tried to perform this experiment without sophisticated ...
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1answer
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What happens at an atomic level that allows us to see objects that are only in the same order of magnitude as visible light's wavelength?

By virtue, humans eye can only see EM wave in the visible light region. From my understanding of 'why we see things', it is because light reflect off an object and the lights' diffraction patterns ...
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Striations in Kundt's tube

Is there some modern calculation of the distances of the striations appearing when experimenting in a tube of Kundt with different powders (sand, cork, etc) sound frequencies and amplitudes? ...
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Bell With Fast Group Velocity

Is it possible to construct a bell where the group velocity going out the opening along the center axis is faster than the speed of sound? What would the ideal shape for such a bell look like as a ...
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2answers
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What makes the disturbance in Electromagnetic waves move.?

I get that changing electric field will have a curly changing magnetic field and changing magnetic field will have curly changing electric field. So when we move a charge up and down, electric field ...
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How does Melde's string behave at the limits of the string?

At the limits of melde's string of length $L$, the expression of the stationary sinusoidal signal $$s(x,t) = y_{0}sin(Kx+\psi)sin(\omega t + \phi)$$ has to verify two conditions : 1/ $s(x=0, t) = 0$ ...
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1answer
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photon emission by the acceleration of electrically charged particles

I understand why the acceleration or deceleration of an electrically charged particle creates a ripple in the existing electric field, which is tantamount to an electromagnetic wave. However, I am not ...
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2answers
136 views

Do electromagnetic fields have inertia? Or, what sets the speed of light?

In all mechanical waves, there is a restoring force and an inertial influence. For example, a plucked string oscillates because the restoring force brings it back to being straight and then the string'...
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2answers
61 views

Why does the intensity of light decrease as you move away from a particular point (described in question)?

I am trying to understand why the intensity of a light wave spreads out along a "back wall" which is near a light source (assume of a narrow bandwidth, ie. red LED). From our experience the answer is ...
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0answers
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What is the suitable form of plane wave expansion?

This question is in Acoustics area. Consider we have a common progressive monochromatic plane wave which is going in an ideal fluid toward an object. The point is that object has symmetry in terms of ...
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2answers
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Why radio waves from radio-stations don't interfere with each other?

I know that radiowaves from radiostations are modulated either F.M or A.M . Lets suppose they are F.M and one has carrier wave frequency of 100 Hz and other 200 Hz they have F deviation of 20Hz/V . ...
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Surface acoustic wave devices, is this a resonance effect or forced oscillation?

I have been thinking about SAW devices the the way the inter-digital transducers (IDTs) launch acoustic surface waves. But I am unclear whether this is a resonance effect or forced oscillations. As ...
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1answer
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How does polaroid filter work at the atomic level? [duplicate]

I know it works by blocking electric or magnetic component of wave while allowing other but what happens at the atomic level , do the atoms absorb the electric component e.g by excitation of electrons ...