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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Wave hitting a boundary with a mass on it?

If we have a transverse wave that is infinite in the $-x$ direction and terminate by a mass $m$, that is allowed to move in the $y$ direction at $x=0$ as shown in the diagram below: I think we can ...
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77 views

Refractive index and electric susceptibility

Suppose we have a complex refractive index $n_{ref}=n+ik$ whose value is given at a precise frequency $\omega_l$ from experimental data. We know that the imaginary part is responsible for the ...
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1answer
53 views

Confusion in understanding wave number

The wave number is the number of complete wave cycles in a meter. So, $$K = \frac{1m}{\lambda}$$ and also, $$K = \frac{2\pi}{\lambda}$$ so according to both of the above equation how is $$2\pi ...
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4answers
754 views

Does increasing the tension on a string also increase the density?

Consider a string under tension, for example, a string on a guitar. When a guitar string is plucked, it vibrates at a certain frequency. When the tension on the string is increased by twisting the ...
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5answers
125 views

Does “apparent frequency” mean the Doppler effect is not an actual physical effect?

When discussing the Doppler effect, we use the word "apparent frequency". Does that mean that the frequency of sound is still that of the source and that it is some physiological phenomenon in the ...
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0answers
24 views

Formation of standing waves in a flume

Having observed standing waves in a flume when the Froude number > 1, I'm unsure how they form at this flow speed. My understanding of standing waves is that it requires equal waves traveling in ...
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2answers
82 views

Derive Equation for Position of Antinode

I'm not sure what to do for this. The equation for standing waves on a string is given by: $$ y=2A\sin{(kx)}\cos{(\omega t)} $$ Use this equation to derive an equation for the position of the ...
4
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2answers
77 views

Can gravitational waves resonate?

Can gravitational waves resonate? - Perhaps by creating standing wave interference in a cavity? Could that feasibly happen either in nature or by engineering?
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2answers
35 views

non diffracting waves

I came upon a proposed solution for a surface wave which was claimed to be a non diffracting wave. The wave at $z=0$ and $x=0$ (which is the propagating direction) is $E_z(0,y) = ...
2
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1answer
59 views

Why is the number of phonon modes in a solid restricted to a finite value?

Kittel's Thermal Physics (Amazon link) makes the statement: There is no limit to the number of possible electromagnetic modes in a cavity, but the number of elastic modes in a finite solid is ...
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1answer
44 views

Paradox of wave energy

Imagine that a wave with energy $E$ is given. as we know $E$ is relevant to the $A^2$($A$ is amplitude) now consider another wave (as same as the first one) and these two wave having a constructive ...
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1answer
155 views

Phase velocity greater then the speed of light?

It is my understanding the the phase velocity of a wave can be greater then the speed of light. So imagine we had a wave packet consisting of a single sinusoidal wave; $$y=sin(\omega t-kx)$$ Then ...
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2answers
36 views

Physical meaning of non differentiatiability of $y(t)$ at a point of an elastic medium

Consider two waves $y_1,y_2$ travelling in opposite directions with equations $$y_1(x,t) = A \sin(\omega t - kx) \\ y_2(x,t) = A \sin(\omega t + kx) $$ That create the following standing wave ...
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0answers
22 views

Generation of electromagnetic waves [duplicate]

I came across this while searching about generation of electromagnetic waves-Does this mean that if I vary the electric current following through a conducting wire, it will radiate electromagnetic ...
0
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1answer
60 views

If the phase velocity is different from the group velocity, why does the high-frequency wave remains fixed with the low-frequency envelope?

Phase velocity is the velocity of the high-frequency wave inside the envelope. While group velocity is the velocity of the low-frequency wave that makes the envelope. If these velocities are ...
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3answers
52 views

Where is the energy stored in destructively-interfering waves?

Let's say we have two waves moving along a string. One of them is represented by the function: $$f_1(t)=\sin(\omega t)$$ The other one is represented by a function: $$f_2(t)=-\sin(\omega (\tau-t))$$ ...
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0answers
56 views

General solution of the four-vector with each component satisfying the wave-equation

Maybe this is more appropriate for Math stackexchange, but this question regards the solution we use in order to find representation for massive / massless spin-1 particle. When $$(\Box + m^2)A_\mu = ...
4
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1answer
167 views

Solution of the wave equation [closed]

I am dealing with the solution of the wave equation in two different cases represented in figure by Case A and Case B. The two figures were obtained by shining a slab with an incident wave coming from ...
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0answers
35 views

What does invariant exactly mean and how does it get the invariant?

I have read many journal about simulation of regularized long wave. In numerical test section,many researcher use invariant of mass,momentum and energy to check accuracy of their method but i found ...
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1answer
47 views

can a wave on rope placed away from gravity go on forever?

we can make waves on a rope like we produce waves on a whip. assume that my rope(which is pretty long) is in space and i produce a wave on it at a point the rope is connected at the two ends. would ...
4
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2answers
420 views

Reflected and refracted light have same frequency as that of the incident light frequency. Why?

My text book says- When a monochromatic light is incident on a surface separating two media, the refracted and reflected light both have the same frequency as the incident frequency. Can anyone ...
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0answers
30 views

Resolving multipath interference when modelling radio wave propagation

I am creating a raytracer to model the propagation of radio waves from a simple router. I am assuming that the rays have a frequency of 2.4GHz and a velocity of the speed of light. The router has an ...
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3answers
135 views

What is meant by phase, phase difference, in (and out of) phase in wave terminology?

What is meant by phase, phase difference, in (and out of) phase in wave terminology? How do you get the relation $$y=A\sin(\omega t + \phi)?$$ Since the graph of sin function is identical to that of a ...
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2answers
65 views

The Frequency of a Trill

My music teacher recently pointed out to me that, when performing a trill (alternating between two notes very quickly) the finger for the higher note should be placed slightly lower on the string than ...
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1answer
69 views

Why can't we define a unique wavelength for a short wave train? [duplicate]

Here we encounter a strange thing about waves; a very simple thing . . .namely, we cannot define a unique wavelength for a short wave train. Such a wave train does not have a definite wavelength; ...
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1answer
173 views

Are reflection and transmission coefficents real or complex?

Is it common practice to give reflection and transmission coefficients as the ratio of the respective waves with respect to the incident wave when written in complex form or real form? I have seen ...
2
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1answer
60 views

Can ultrasonic signal be guided through a tube?

I have an industrial application using an ultrasonic sensor to detect whether transparent film is present in a plastic ring. Ring minimum diameter is > 30mm. Sensing distance is 90mm. Sensor ...
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2answers
166 views

Why does light travel as waves? [duplicate]

Why does light travel as waves instead of say just a straight line? What are the forces that make a light photon travel in a wavelike pattern?
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0answers
37 views

standing wave formation in a string of varying density

What will be the condition of standing wave formation in a string fixed at both end if density of string is uniformly increasing ?
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0answers
181 views

ratio between conduction current and displacement current

First, recall that Maxwell displacement current for a plane wave is $$ \vec j_D = \epsilon \partial_t \vec E = \epsilon \partial_t (\vec E_o cos(\vec k \cdot \vec r - \omega t)) = \epsilon \omega ...
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0answers
36 views

Does superposition principle apply to the velocity of each particle in a wave?

Superposition principle can be applied to find the net displacement of a particle when two waves interfere. But can it be applied in case of velocity? If so, then what happens to the velocity of the ...
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5answers
2k views

Why are electromagnetic waves called waves even though they don't travel through a medium?

If waves are defined as the oscillation of a medium, why are electromagnetic waves called waves as they do not need a medium to travel through?
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1answer
37 views

Natural frequencies

It's defined as the frequency that an object vibrates at when there is no driving force. What's a driving force? IS the natural frequency the frequency at which the atoms inside vibrate? People ...
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3answers
196 views

Definition of a normal mode?

What is the formal definition of a normal mode for a string? And how does this relate to the definition from e.g. wiki that seem to be applied to discrete systmes of particles only? Also on a string ...
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2answers
95 views

Why do we lose signal in elevators? [duplicate]

Whenever I am talking on my phone and walk into the elevator the call drops as soon as the doors close, and also the WiFi signal completely stops. Why does this happen? Note: I am asking this ...
2
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3answers
73 views

Sound waves during day and night

A man stands on the ground at a fixed distance from a siren which emits sound of fixed amplitude . The man hears the sound to be louder on a clear day than on a clear night. Why?
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1answer
40 views

Why do dispersive waves get wider?

Consider the two waves $$y_1=Acos(\omega_1 t+k_1 x), \tag{1}$$ $$y_2=Acos(\omega_2 t+k_2 x), \tag{2}$$ where $\omega_i=k_iv(k_i)$ for $i=1,2$ so we have a dispersive medium. Then if we take their ...
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1answer
36 views

Is difference in wave number always small?

Over the last few days I have been looking at a derivation of group velocity. The derivation is the one shown in this question Deriving group velocity. I have seen this derivation in many places, and ...
2
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2answers
226 views

Why do objects have resonance at natural frequency?

What actually is a natural frequency for an object and what makes it vibrate with increased amplitude when coupled with an external oscillator that matches the natural frequency?
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1answer
70 views

Derivation of group velocity?

In the standard simplified derivation of group velocity (which can be found here) we use two waves $$y_1=A\sin(K_1x-\omega_1 t)$$ $$y_2=A\sin(K_2x-\omega_2 t)$$ In the proof we then get ...
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0answers
112 views

What happens to the velocity distribution during constructive interference?

Two pulses(one inverted & having velocity in the opposite direction) moving towards each other with same wavelength & amplitude after undergoing destructive interference do reapper. Why? ...
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1answer
891 views

Why can't transverse waves travel through a liquid?

Can someone explain why a longitude wave can pass through the liquid, but a transverse wave can't. And can someone recommend some good animation of these processes.
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1answer
69 views

Why doesn't the speed of the wind have an effect on the apparent frequency?

A boy is standing in front of stationary train. The train blows a horn of $400Hz$ frequency . If the wind is blowing from train to boy at speed at $30m/s$, the apparent frequency of sound heard by the ...
4
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0answers
88 views

Mathematical defintion of a standing wave? [closed]

I know that a standing wave is the superposition of two waves of equal amplitude and wavelength, moving in opposite directions. But I am looking for a more mathematical defintion of such a wave. The ...
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4answers
142 views

Energy of a wave and Planck formula

Especially from this post I understand that the energy of a wave is directly proportional to the amplitude of that wave squared. Therefore, we can determine the total energy of a wave by summing the ...
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1answer
69 views

Why is it mandatory to make the string taut/stretched for sending pulse/wave?

In order to send a pulse and to propagate it, the string must be under tension.$^\text{1}$ Why is the tension necessary? Why should the string be stretched/taut for the transmission of the pulse? ...
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0answers
38 views

Fresnel equations of S and T waves and Isofrequecy Curves: Feeling confused

First of all sorry for my (probably) bad english. I've been studying propagation of light in anisotropic media from the Born and Wolf and from Landau "electrodynamics in continuous media" and I'm ...
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34 views

Will a longitudinal wave propagate “forever” in a tube?

I understand that the wave will lose energy due to "friction" between the, lets say, water molecules, but in my mind at least the biggest loss of energy in a wave is normally the dispersion of it. ...
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1answer
159 views

What sort of waves are produced by tuning forks?is it transverse, longitudinal or both?

We often know tuning forks are used to to produce wave in various experiments that we do in lab. but the matter of concern is what sort of waves are produced by it? is it transverse, longitudinal or ...
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1answer
90 views

Mechanism of propagation of pulse in a string

If you give one end of a stretched string a single up-and-down jerk, a wave in the form of a single pulse travels along the string. This pulse & its motion can occur because the string is under ...