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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What makes a wave dispersive?

Water waves are dispersive ( longer wavelengths travel faster ) but sound waves in air are not, otherwise we would listen first the high frequencies and the low frequencies after. What decides if a ...
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3answers
70 views

Derivation of the group velocity

I know that the group velocity of a light pulse is defined as $$\begin{split}v_g&=v_p\left(1+\frac{\lambda}{n}\frac{dn}{d\lambda}\right)\\ ...
3
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1answer
67 views

Why do water waves with longer wavelengths travel faster?

When wind blows over the sea, it excites a range of wavelengths. Why do longer wavelengths travel faster?
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1answer
17 views

Pressure Inverting Reflection of a Sound Wave

How would the frequency and energy of a pressure inverted sound wave compare to the frequency and energy of the original sound? Would it sound any different?
0
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1answer
46 views

Interference of light waves question

We were recently asked to solve a question in class which goes as follows: In a modified Young's double slit experiment, a monochromatic uniform and parallel light beam of wavelength $6000$ ...
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3answers
273 views

Why a ship can't pass through its own wave?

This is a photo of a container vessel. All container vessels are long because they are cruising at high speeds. When a ship is sailing it creates waves. When the wavelength of these waves equal the ...
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20 views

Laplace's correction

In Laplace's correction volume is raised to gamma which is a ratio of molar heats on different conditions. I want simply know that why gamma does not describe any thing about pressure but volume ...
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0answers
20 views

What is the relationship between the size of a slit and wavelength in diffraction? [duplicate]

Almost everywhere I see the statement that diffraction gets stronger when the size of the slit is comparable to the wavelength. I would just like to know the logic behind. Could anyone help me please? ...
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0answers
14 views

Scale analysis for the vertical component of the Boussinesq equation to obtain a complete hydrostatic relation

This is actually an exam question which i have been trying to solve for my studies. Consider the Boussinesq vertical equation: \begin{align} \frac{\partial \widetilde{w}}{\partial t} = - ...
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0answers
21 views

Intensity of interfering light waves

I had a conceptual question above light wave interference. Suppose that two light beams, each of an irradiance $I$ interfering on an area $A$ of a screen, such that all of the light from each beam ...
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1answer
17 views

Progressive and Stationary Waves Amplitudes confusion

In my mechanics lecture, my professor mentioned that standing waves have nodes and antinodes, which is correct. Then he mentioned that in progressive waves, all the points have the same amplitude. ...
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31 views

How can there be E and B fields inside waveguides?

A hollow waveguide that is made of conducting material allows for the existence of an electromagnetic wave inside it which propagates from one end to the other. However, conductors are known to ...
2
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1answer
56 views

What causes electromagnetic waves to propagate in free space?

In free space, $\rho=0$ and $J=0$, so there are no electromagnetic sources/sinks. Maxwell's equations thus reduce to: $\nabla\cdot E = 0$ $\nabla\cdot B = 0$ $\nabla\times E = -\frac{\partial ...
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1answer
52 views

Can there be a wave function that is physically possible but is non differerentiable (maybe even non-continous)?

The definition of a wave function demands continuity and differentiability so that it can satisfy the Schrödinger Equation. My question is whether this assumption is necessary for reality. Does ...
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1answer
25 views

Diffraction grating (finding number of emission lines)

I came across a question on isaacphysics.org where youre given information about a diffraction grating, the spacing of the gaps and the colour and location (in degrees) of 8 different maxima, of four ...
0
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1answer
42 views

2D standing wave

When we have 1D standing waves, we can write them as the sum of two propagating wave in opposite directions that give the formula $\sin(kx)\cos(wt)$. When I try to do this for 2D waves (I mean 2D by ...
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2answers
38 views

Wave reflection

I have a simple question on wave reflection. I know that if I have a progressive monochromatic EM wave and a mirror, the reflected wave will be opposite in phase on the mirror to assure a total E ...
0
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1answer
36 views

Newtons corpuscular theory

I am learning about the history and evolution of certain physics theories, one being Newtons corpuscular theory. I am reading that Newton predicted the corpuscles, which make up light would travel ...
0
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1answer
34 views

Why must we use mode locked lasers?

Quick question: If I have a laser cavity with a bunch of harmonics under the gain curve: Why do I not always get a pulsed laser? EG: I mean since these harmonics exist in the cavity arn't they ...
0
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1answer
36 views

Does the frequency of a organ pipe changes with its diameter? Explain

I am confused a bit does the frequency of a organ pipe have relation with its diameter or not.
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2answers
72 views

Wavelength and Frequency (Wave travel)

It is true when a wave is traveling in a constant velocity, there is an inverse relationship between a wavelength and frequency. For example, if a wavelength is increasing, frequency should decrease ...
5
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1answer
649 views

Liquid wave faster than sound in the above gas: possibility implications

I recently heard that tsunamis (meaning "harbour wave") can travel over 800 kilometres per hour (500 mph), not so far from the speed of sound in the air. May it happen, in general, that a wave in a ...
0
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1answer
14 views

Working out the speed of a object by its frequency and a superposition wave?

Say you have 2 loudspeakers facing each other and they are separated by 20m, but are connected to the same oscillator and so both have a signal frequency of 800Hz. I calculated the separation of the ...
2
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0answers
62 views

What happens to Newton's Third Law during the reflection of a pulse from a free end?

Well, it is known that a pulse gets inverted when it gets reflected from a fixed support while the polarity of the pulse remains same when the incident pulse gets reflected from a free end. However, ...
4
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1answer
46 views

Resultant intensity of two waves

For long I've been thinking about this issue, but ended up with nothing : Suppose you have a point source $S_1$ sending a spherical wave in space of equation $\phi=\dfrac{A_0}{r}\sin(kr-\omega t)$ ...
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0answers
26 views

What would happen if we try to emanate sound waves from a conic surface? [duplicate]

Say we want to emanate sound waves through a conical surface, what would happen at the tip? How would the waves be?
2
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2answers
64 views

How can 2 EM waves null each other at a point but continue to propagate?

how can 2 EM waves (travelling in opposite directions) null each other at a point in space but continue to propagate beyond the point in space where they interact to null each other?
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2answers
39 views

Double slit with opposite circular polarizers

Let's say I'll send linearly polarized light onto double slit but in front of one slit I'll have quarter wave plate and before the other I'll have 3/4th wave plate (half+quarter? minus quarter?) ...
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0answers
43 views

Why call it a particle and not a wave pulse?

My physics textbook says that photoelectric emission provides conclusive evidence for the particle theory of light. Apparently, since photoelectric emission only works at certain frequencies, we can ...
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0answers
45 views

What will be the shape of this graph at $t= \frac {T}{4}$

Consider the following variation with distance x and displacement y of the string at $t=0$ Then what will the shape of the graph be at $ t= \frac {T}{4}$? My Attempt: I feel that the peaks of ...
0
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2answers
34 views

Relation between wave functions $f(x-vt), f(t-x/v), f(kx-\omega t)$

I was struck by an answer to this question that made me think about various ways to write a solution to a wave equation. One can write $f(x-vt)$ or $f(t-x/v)$ (as noted in an answer to the above) or ...
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3answers
3k views

Why do travelling waves continue after amplitude sum = 0?

My professor asked an interesting question at the end of the last class, but I can't figure out the answer. The question is this (recalled from memory): There are two travelling wave pulses moving in ...
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1answer
34 views

Standing wave confusion

To form a standing wave, two coherent waves must travel in opposite direction. But is it it necessary for them to have the same amplitude and no phase angle difference?
0
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2answers
242 views

What is the amplitude of the electric field in a laser?

I'm looking for reliable informations about the amplitude (not the intensity), in volt/meter, of the electric field in a typical laser. Or in other words : what are the typical amplitudes of the ...
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0answers
21 views

What would the effects of the GW150914 gravity wave burst be on observers much closer that 1.3B LY? [duplicate]

The effects of the GW150914 gravity wave burst were barely observable with state of the art instruments, i.e. LIGO. What would the effects of GW150914 gravity wave burst be on observers much closer ...
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8 views

Kelvin Wake Pattern discrete approximation

I read the wikipedia article about (Kelvin) Wake patterns and stumbled over this graphic: I understand it as if every of these circles is a disturbance measured at a time $t$ and the radius of ...
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0answers
30 views

Why is the wave equation useful in the real world [duplicate]

The one dimensional Wave Equation $u_{tt}=c^2u_{xx}$ is used to describe wave propagation etc. But how does solving this equation specifically help us in the real world?
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0answers
39 views

How Can LIGO or Any Such Gravitational Wave Detector Detect Displacement Which Are Billionth of Times Smaller Than Mirror Tolerances

I am very excited about GW150914, the maiden direct detection of gravitational waves. Since i am naive about experimental nitty-gritties, allow me to pose a naive question: After all the interference ...
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1answer
61 views

Wave equation in classical mechanics!

We represent the wavefunction of any wave on the string as $$y=f(x-vt),$$ where $v$ is velocity of the wave and $x$ is distance from origin and $t$ is time taken to reach the given point and $y$ ...
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1answer
35 views

Optics of stationary waves

could anybody tell me how it Works if it comes to stationary waves created on the surface of water jet and optics? there are some crests and troughs which work like lenses, but if you have water jet, ...
0
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2answers
47 views

Wave intensity and superposition

Let us say we have 2 point sources of sound. My question is how do we consider the intensity to vary according to position? Let's say both have same amplitude, frequency and speed, just different ...
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1answer
28 views

Wave generated with particle excitement

To my understanding, an electromagnetic wave(infact two perpendicular fields) will be emitted when a particle(e-) shifts from higher energy orbital to lower energy orbital but what would be the ...
0
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1answer
27 views

Wave speed question wave equation given in terms of exp [closed]

Question A wave propagating along the x axis . The displacement of the particles is along the Z axis at t=0 is given by Z= exp[-(x+2)^2] where x is in metres . At t=1 Z= [-(2-x)^2] find the speed ...
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4answers
87 views

Is it possible for a harmonic to be louder than the fundamental frequency?

Using most sound equations, it is quite clear that increasing frequency decreases amplitude, but is there any example where this is not true?
7
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1answer
337 views

What was Newton's own explanation of Newton's rings?

What was Newton's own explanation of Newton's rings? Newton advocated a corpuscular theory of light, but his rings would most conveniently be explained by a wave theory. How did he explain his own ...
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2answers
37 views

Why would a decreased length mean a higher frequency of sound?

This is in terms of the Water Bottle Lab: adding water (effectively decreasing length) to a bottle and finding its fundamental frequency at different lengths/amounts of water. I understand what ...
0
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4answers
49 views

About speed of sound?

Even though Speed of sound at room temperature is very large equal to 342m/s yet it does not cover that much large distance when we speak. What are the conditions at which sound really travel 342m in ...
2
votes
3answers
67 views

Baryonic acoustic oscillations: Why are there standing waves in the CMB?

On page three of the following http://www.quantumfieldtheory.info/CMB.pdf, Klauber talks about the formation of standing waves from acoustic vibrations in the early universe. He claims that they form ...
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1answer
37 views

3D Standing wave [closed]

I need to derive an equation (like a vibrating string) of a 3D vibrating object having a mass ‘m’(object itself made of bunch of closely packed particles, in-between the particles there should be an ...
0
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0answers
22 views

Given Tension and the wave equation, how do you find the linear density?

I am given that the equation of a transverse wave of a string is y(x,t) = 2.00mm(sin(25.1rad/m)x-(415 rad/s)t) and the string is under 18 N of tension. From the tension, I got that the string is ...