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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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Why do musicians stretch the strings of their string instruments?

I came across this simple problem:´ A violin string has a density of $\rho=4.0\times 10^{-4}\space Kg\space m^{-1}$ and a length $L=0.33m$, and we want it to vibrate at a frequency $f=660Hz$, what ...
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Effects of oscillating objects on doppler shift on moving objects

For some reason I've been thinking about this for a couple of days: Say I have two aircraft almost identical in weight and shape. Although one of the aircraft has a propeller that can rotate at any ...
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Snapshot and history graph of wave

[] I don't understand why the wave is moving to the right, the x graph is showing downward movement and the right graph is showing upward with time. please explain better than the statement in the ...
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What causes the wave velocity of longitudinal waves in a spring to changes as its length changes?

This video shows the velocity of longitudinal waves changing in a slinky spring as its length changes: https://youtu.be/y7qS6SyyrFU?t=17 Something else responsible for the change in velocity ...
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How can we relate the wavelength of light to the length of a transmission line?

For the wavelength in free air we have $\lambda = \frac{c}{f}\, [\rm{m}]$, but how does it relate to the length of a transmission line? My question is because of the following example from this site: ...
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Affect of amplitude and distance on intensity [on hold]

A point source emits sound waves of amplitude A. The sound intensity at a distance d from the source is I. What is the sound intensity at a distance 0.5D from the source when the source emits waves of ...
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What happens to the pressure time graph when two musical instruments play at the same time?

I'm learning acoustics for the first time and I'm having trouble picturing what the pressure time graph would look like when two instruments play together. https://newt.phys.unsw.edu.au/music/flute/...
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Einstein's frozen wave (Does it mean stationary wave)?

Here's the quote from Stephen Hawking's latest book. At the age of sixteen, when he (Einstein) visualised riding on a beam of light, he realised that from this vantage light would appear as a ...
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Are there any differences between the standing wave diagrams of two non-transposing instruments? [on hold]

For example, a cello and a flute are both non-transposing instruments. Thus, they both have harmonics at the same frequencies. Will there be any differences in their pressure time graphs then?
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Wave pulse in 3D

For a 1D wave equation: $$\frac{\partial^2 \psi}{\partial x^2} = \frac 1{c^2} \frac{\partial^2 \psi}{\partial t^2}$$ We can write a solution of the form: $$Ae^{-b(x-ct)^2}$$ representing a localized ...
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A question on the properties of wave equations

When you change $$y(x,t)=A\sin(kx-ωt+φ) $$ into $$y(x,t)=A\sin(2kx-2ωt+φ), $$ does it double the wavelength because $k$ changes into $2k$ and double the frequency since ω is doubled? If this is ...
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Lack of invariance of relativistic doppler effect for inertial frames?

The equation for the relativistic doppler effect in a medium where waves travel at speed $c_m$ is $$\frac{f_r}{f_s} = \frac{c_m - v_r}{c_m-v_s}\frac{\gamma_r}{\gamma_s}$$ My question is whether this ...
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If 2 spaceships approaches each other at 0.99c, how much blue shift would they see? [on hold]

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 ...
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2answers
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Does a string vibrating with hard boundaries contain harmonics of the fundamental frequency?

When the string of a violin is plucked, the resulting sound contains harmonics of the fundamental frequency. Is this an inherent property of a string with hard boundaries vibrating? Does an ideal ...
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Why are partial derivatives necessary when deriving the equation for a vibrating string? [migrated]

AFAIK, partial derivatives made it to the forefront as a result of coming up with an equation for a vibrating string i.e., 1D wave equation. From purely a physical phenomena to math mapping POV: Why ...
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Does bending a piece of steel change the speed of sound in it?

Specifically, I have a student investigating sound produced in a helical spring (slinky) when struck. When it is struck it produces a sound that changes in pitch - from very high to quite low. Also, a ...
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1answer
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Sound wave equation: Neumann boundary conditions

In this paper it's described the solution of the damped wave equation in cylindrical coordinates $$ \nabla^2\left(c^2\rho_1+\nu\frac{\partial\rho_1}{\partial t}\right)-\frac{\partial^2\rho_1}{\...
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Exact form of the damped wave equation

The undamped wave equation has the standard form \begin{equation*} \frac{\partial^2 \psi}{\partial t^2}=c^2\nabla^2\psi \end{equation*} while the damped wave equation is frequenly found written in ...
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What is the definition of pitch of a helix (spring) in terms of slope?

This question is linked to another question that I asked in Math section. I think this specific part is more relevant to physics. I have designed a 3D helix structure. The radius is constant but the ...
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2answers
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How to mathematically express permittivity as a function of frequency

I am a amateur physics student. I am modelling the wave propagation of an EM wave at different frequencies through water placed between two acrylic rectangular materials using COMSOL. But since the ...
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Energyeigen modes of a vibrating string [closed]

Energyeigen modes for the vibration of a string fixed at both ends plucked at the middle
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Behavior of wave fronts as it crosses a convex lens [closed]

There is a explanation given in my book regarding behavior of wave fronts as it crosses a convex lens( i.e refraction of plane wave by a convex lens). Here is the thing that's written :- "When a ...
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1answer
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Beat frequency with tuning forks

If you have two tuning forks and you know that one tuning fork is 305 Hz, and when the tuning forks are pinged together you get a beat frequency of 6 Hz, then you know that the other tuning fork is ...
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Amplitude of a wave: will it be an overlap of two waves or is there another reason?

For a wave with initial conditions and with a velocity = 1.00 m / s the following graph was obtained: The spatial domain is [0; 50] m and the time domain is [0, 50] s. The wave reaches the boundary ...
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1answer
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What does electromagnetic wave literally look like? [closed]

What does electromagnetic wave literally look like? Some people on the Internet called electromagnetic wave as something that has literally only two dimensions, I think it is because of this over-...
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Energy density of a plane progressive wave equation [closed]

Equation of energy density of plane progressive waves
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Solutions to an Underdamped Oscillator

In many of the books talking about damped Simple Harmonic Motion, the underdamped Oscillator is treated as follows: We have Newton's Second Law Equation as - $$m\ddot{x} + r\dot{x} + sx = 0 $$...
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Hello. I want some help. Can you help me to do this question? [closed]

The superposition principle states that if two or more waves are traveling in the same medium (air, water, and so on) the resulting wave is found by adding together the displacements of the individual ...
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1answer
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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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Mechanical Wave propagation in fluids

My book says that since a transverse wave in strings involves shearing/tangential stress, the same cannot propagate in fluids as they yield to shearing stress. Hence the propagation of waves wherein ...
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Clear formula for water penetration by wave frequency

I want a clear formula for clear water (and salty water) penetration by giving only the radio wave frequency . I searched the web , the formulas on the web are so complicated . Are there any simple ...
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2answers
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Which book would you recommend for a dummy wanting to start studying acoustics, out of interest?

I've been very into acoustics lately, specifically the harmonic series. I find it fascinating how the harmonic series works as a sort of guideline to harmony, and how we base tuning systems on trying ...
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Is there a name for this wave effect?

So I was using this wave simulation (https://phet.colorado.edu/sims/html/wave-on-a-string/latest/wave-on-a-string_en.html) when this happened; using the settings: Oscillator, High tension, no damping. ...
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2answers
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Young Double Slit Experiment Formula - Nodal Lines

Some sources use the formula $\frac{X_n}{L}= (\frac{(n-\frac{1}{2})λ}{d})$, while other sources use $\frac{X_n}{L}= (\frac{(n+\frac{1}{2})λ}{d})$ when talking about destructive interference. Why is ...
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1answer
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Damped mechanical wave

a string with density $\rho$ and tension $T$ is bound at it's two ends at $x=0$ and $x=L$. there is a force acting on the string proportional to the velocity $F(x,t)= -2\gamma \rho \dot \psi(x,t)$ ...
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Dual nature of light [duplicate]

Light behaves as both particle as well as wave according to dual nature of matter. But if light behaves as wave then which type of wave - longitudinal waves or transverse waves?
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1answer
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Why do two masses connected to each other by a spring have the same frequency of oscillation?

Why do two masses, connected to each other by a spring, and each connected to a wall by a spring, have the same frequencies of oscillation when perturbed? In solving for the motion of the masses, ...
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Why exactly does diffraction occur?

Why do waves that were traveling in a straight direction change direction when passing through an opening? I thought that the waves (red arrow) when colliding with the wall bounce in the opposite ...
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2answers
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What is the model for wave reflection?

in this animation from the Fresnel equation wiki we can see a wave bouncing back in the "negative" compared to the "positive" incoming wave. What physics model govern such behavior in transverse waves?...
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1answer
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Paraxial approximation in nonlinear optics [closed]

I have a question about the paraxial approximation in nonlinear optics, it is different from the one in linear optics. and i'm confused about the difference between them, can anyone clarify this ...
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1answer
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Why can't ultraviolet light pass through glass?

What factor determine whether a body behaves like a transparent object for EM waves of a particular frequency?
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1answer
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Guitar strings struck out of phase

Do guitar strings struck out of phase with one another force each other to begin vibrating in phase with one another? I ask because wouldn’t chords sound more dissonant from time to time if this did ...
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Can a pressure wave travel faster than a material breaks?

Consider a shock wave travels through a solid (M) which causes a 4g acceleration. Down below there is an elastic spring (K1) which suppose to support the mass in case K2 will fail. K2 is a rigid body ...
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Why can we distinguish different pitches in a chord but not different hues of light?

In music, when two or more pitches are played together at the same time, they form a chord. If each pitch has a corresponding wave frequency (a pure, or fundamental, tone), the pitches played together ...
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3answers
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energy of a photon for a complex wave

If I use a plane wave of light given by $$E=E_o \sin(\omega t+\phi)$$ for photoelectric effect, then the energy of photon associated is given by $h\nu$ where $\nu=\frac{\omega}{2\pi}$ But suppose ...
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3answers
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In Young's double slit experiment, can there be an even number of maxima in the central envelope maximum?

In Young's double slit experiment, can we get an even number of maxima in the central envelope maximum? If so how and why the regular modelling of the double split interfaces is with an odd number ...
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1answer
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Constructive interference derivation

What is the difference between using $y=A\sin\omega t$ and $y=A\sin(ct-x)$ in a wave formula? I am not a math student and I am not getting this.
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What do wave crests indicate about a boat's speed?

Wave crests spread out behind a boat as shown above. What do the wave crests indicate about the boat's speed? It is increasing. It is less than the speed of the water waves. It is equal to the speed ...
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Sound pitch changes as glass is filled with water. Why? [duplicate]

As a glass is being filled with a liquid (usually water), the sound it produces changes in pitch until it gets full (you can usually hear it when it is almost full). Why does this happen? And what ...
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1answer
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Why does a sound wave on encountering a low pressure region gets reflected with a “phase change of π”?

I am particularly concerned with the reason for phase change of π. This is observed in organ pipes at their open ends. The waves on encountering the open atmosphere(low pressure region) reflects back ...