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.

learn more… | top users | synonyms (1)

1
vote
3answers
170 views

How damaging is light? [closed]

On Surely You're Joking Mr Feynman, when talking about the Trinity test, the author states: the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet ...
1
vote
1answer
45 views

Time dependency of the phase of a single photon

I am wondering if a wave packet of a single photon in the time domaine $$ \psi(t)=|\psi(t)|\; \text e^{\text i \varphi(t)} $$ can have a different $t$ dependence in phase than the simple phase ...
1
vote
1answer
158 views

Wireless electricity through Wi-Fi power signal?

Could there be a method to obtain and send worldwide electricity through WiFi? I mean if we have internet everywhere and only need a WiFi device, can we apply the same to electricity technology? or ...
1
vote
2answers
126 views

Transmission of waves

How do you know if a wave will transmit when it hits a media boundary? Will a portion of the wave always be transmitted when a wave hits a media boundary? My textbook says part of the wave will be ...
1
vote
1answer
42 views

Why would a screen(with touch controls) in a vibrating environment be readable if its refresh rate is dynamically matched with vibrations?

So, I was reading about this Dragon V2 and it has got touch controlled screens, but screen might be unreadable for pilots because of engine vibrations and whatnot. I came across this comment on ...
1
vote
2answers
266 views

Intuitive explanation of the waves superposition

When the two waves collide, why do they pass right through each other? Mathematically it's due to the principle of superposition: the sum of the two solutions of a wave equation is also a solution. ...
1
vote
2answers
78 views

Does a light wave that has been cancelled by another light wave continue traveling forward?

I imagine that if a light wave is cancelled out by another light wave, it would still continue to exist as a photon that is traveling at the speed of light--only without a wavelength. Would it behave ...
1
vote
1answer
99 views

Ratio of energy of normal modes of string

Suppose there's a wave on a string represented by fourier series: $$y(x,t) = \sum_{n=0}^{\infty} (-1)^n \frac{1}{2n+1} \sin(nx)\cos(nct)$$ I know the energy is $\propto y^2 n^2$, where $y$ is the ...
1
vote
2answers
89 views

Is there just one fundamental frequency?

I read simple definitions of the terms frequency, and fundamental frequency, which defined them thus, Frequency: the number of occurrences of a periodic wave during a second Fundamental Frequency: ...
1
vote
1answer
72 views

Convective derivative of oscillating fluid with bulk motion?

I have a fluid $u$, which comprises a zeroth order constant motion $u_0$ as well as a first order oscillatory motion $u_1$. The convective derivative is $$\frac{\partial u}{\partial t} ...
1
vote
2answers
559 views

A difference between Plane Wave and Collimated?

Collimation is clearly in reference to ray($\vec{k}_{xy}$ vector) orientation unlike waterfront continuity( $\phi_{xy}$ phase shift) described by plane-wave. Not to say that one is not directly ...
1
vote
2answers
185 views

Can sound be propagated without initial mechanical interference?

I have researched up a little on sound, and it seems that sound is a mechanical wave that propagates through the air as energy, and that is how we hear it through our ears. Depending on the medium's ...
1
vote
2answers
552 views

A foundational question about harmonic motion : 2 pipes with different length and frequencies [closed]

How to solve the following question? A pipe open only at one end has a fundamental frequency of 256Hz. A second pipe, initially identical to the first pipe, is shortened by cutting off a portion ...
1
vote
2answers
111 views

Why the wave-particle duality cannot be explained as a traveling-standing wave duality?

This would explain why speed and position cannot be measured at the same time, since either the wave would be traveling (speed) or enclosed and standing (position). The act of enclosing it (to be ...
1
vote
3answers
562 views

What is the energy of a standing EM wave? Is it probabilistic?

In a cavity, the standing wave will constructively interfere with itself, so its energy gets higher while the oscillator is still vibrating. Since the vibration time is not a constant value, and ...
1
vote
1answer
111 views

Nonlinear Dirac's Equation?

Are there any nonlinear variations of Dirac's Equation analogous to the Nonlinear Schrodinger Equation, that have been studied and published in any mainstream journals or books? Perhaps such a ...
1
vote
4answers
1k views

Can a wave be two dimensional?

I am having a hard time picturing waves, the image that comes to mind is a bobbing device submerged in still water which generates pulses in all directions (similarly in air). Then how can a wave be ...
1
vote
1answer
44 views

Varying the amplitude of a driven wave

I' d like to know whether varying the amplitude of a system at resonance is possible or not and if it is, how? I've calculated the resonance frequency of a material and I'd like to know the ...
1
vote
1answer
580 views

Factors affecting the size of a shadow

What factors affects the size of a shadow and how would you derive the diameter of a shadow of a circular object on a flat screen?
1
vote
3answers
634 views

How to determine the direction of medium's displacement vectors of a standing wave?

Consider the following problem taken from a problem booklet. My questions are: What is displacement vector? And how to determine the direction of displacement vector at a certain point? Where is the ...
1
vote
1answer
243 views

Definition of energy

What is the definition of energy $E$ given a dispersion relation $\omega=\omega(k)$ where $k=|\vec k|$ and $\omega$ is not necessarily linearly proportional to $k$? What about momentum $\vec p$? This ...
1
vote
1answer
327 views

Why are clouds wavy?

Say you're in an ascending airplane as your 10 year-old son asks you: "Dad, why are these clouds wavy?" Now, say you know a little about gravity waves and the formation of wavy clouds(Maybe I should ...
1
vote
1answer
825 views

How to prove equations for energy of a wave

In my textbook, it says that the energy (I) of a wave, determined by the power of a wave (P) divided by area (A), is determined by the following formula: $$I = \frac{1}{2}\rho v\omega^2A^2 = 2\pi^2 ...
1
vote
2answers
2k views

Questions regarding standing waves

I have two questions regarding mechanical waves. 1) We know that standing waves are created when any wave traveling along the medium will reflect back when they reach the end. But in an open organ ...
1
vote
2answers
546 views

Standing wave and energy flux

Here is a problem I have been asked that I do not know the answer. Consider two ideal wave generators (it can be sound generator or whatever) separated by a distance L and facing each other. At t=0 ...
1
vote
2answers
1k views

Does a cycle (in Simple Harmonic Motion) have to equal 2π?

So, I search for the definition of cycle and I get this in Wikipedia: A turn is a unit of angle measurement equal to 360° or 2π radians (or ...). A turn is also referred to as a revolution or ...
1
vote
1answer
139 views

Waves and information

I'm looking to transfer very simple information using audio waves. One of the approaches I'm looking into is using different frequencies. For example, "command 1" will be transmitted using 500Hz wave, ...
1
vote
1answer
160 views

Time evolution of wave spectrum

A useful way of thinking (not only) oceanic waves is to consider them as a superimposition of linear modes: the elevation η of the sea surface is given by: 1: $\eta({\bf x}, t) = ...
1
vote
2answers
160 views

EM irradiament and multipoles

Why in the irradiament mulipoles of Lienard-Wiechert's potential we say that electric quadrupole give a contribute of the same order of the magnetic dipole? How can we see it from their equations? And ...
1
vote
2answers
106 views

Why intensity of light(wave) is proportional to the square of its amplitude?

I am confused, Classical wave theory says that Intensity of the light(wave) is the proportional to square of the amplitude. How intensity is proportional to the square of the amplitude?
1
vote
1answer
49 views

D'Alembert Equation and standing wave

As we know the d'Alembert Equation is $$ \frac{\partial^2\psi}{\partial x^2}=\frac{1}{c^2}\frac{\partial^2\psi}{\partial t^2} $$ for an undimentional string. Now if we seek standing wave ...
1
vote
1answer
39 views

Energy Proportional to the Square of the Amplitude

I don't understand how the energy of a wave is proportional to its amplitude squared...For example, if we consider simple harmonic motion at the maximum displacement, there is no kinetic energy and ...
1
vote
1answer
41 views

Question regarding charge and acceleration

From a stationary charge electrostatic fields arise. From a moving charge, magnetostatic fields arise. From an accelerating charge, EM waves arise. So i wonder -- what about a non-constantly ...
1
vote
1answer
32 views

In a noiseless environment, how accurate do today's transmitters send EM waves?

Suppose that there is no external noise in the environment. How accurate are today's TEM wave transmitters in such a case? So if we want to send $200\cos(1000\pi t)$, can transmitters send exactly ...
1
vote
2answers
85 views

Wave equation - dissipation

The book states that the wave equation assumes no dispersion and no dissipation, with dissipation defined as a loss of energy and thus a diminution of amplitude. How can a spherical wave be described ...
1
vote
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 ...
1
vote
1answer
160 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 ...
1
vote
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? ...
1
vote
1answer
110 views

Why is beat described as a “relatively slow amplitude-modulation of oscillation”?

Excerpts from A.P.French's Vibrations & Waves: . . . It may be seen that the combined displacement can be fitted within an envelope defined by the pair of equations$$ x = 2\mathit{A} ...
1
vote
1answer
35 views

Pressure wave in a cup of tea casued by a bubble burst

Assume there is a cup of tea with bubbles formed on its surface by the inner wall of the cup. If one of the bubbles bursts, it causes a wavefront travelling on the surface of the tea. Is this wave ...
1
vote
1answer
110 views

How to draw waves in X and Y position like this oscilloscope example?

I would like to know how to "draw sound" so i could achieve shapes like the ones in this video: http://www.modularsynth.ru/en/2014/01/24/ed120_chaotica/ I have programming background ( as in: i ...
1
vote
1answer
30 views

Electron orbitals and the circular membrane vibrations

I just stumbled across the fascinating analogy between electron orbitals and the fundamental waves of a circular membrane in Wikipedia. Now the weird and arbitrary looking orbitals don't look so ...
1
vote
1answer
55 views

Does Red shift affect electron waves? [duplicate]

According to the De-Broglie Wave Hypothesis an electron can be considered to be a wave. Red Shift occurs due to the expansion of space(Cosmological red shift), which must expand even on the scale of ...
1
vote
1answer
61 views

What happens in extrema cases of red shift?

Red shift is the increase in the wavelength of an electromagnetic wave as it travels through space. If the wave travels for a time long enough can its wavelength increase so much that it becomes ...
1
vote
1answer
92 views

Abstract concept of wave propagating on a string

I'm a real beginner in physics with a really basic doubt about waves. Suppose i have a string ( perfect elastic material ) whose left-end i can manipulate ( i can change its heigth ) and whose ...
1
vote
1answer
40 views

Water wave packet variance

Consider the following quantity, $$I = \int x^2|\eta(x)|^2 \ dx,$$. For $\eta(x)$ a solution to some linear equation, we have $\eta(x) = \int a(k) e^{ikx} \ dk$ where, for $\eta$ to be real, we ...
1
vote
1answer
101 views

How does a non-diffracting beam form from a converging ring of illumination?

I am trying to intuitively understand the basics of the supplementary text of a recent publication from Eric Betzig's group on lattice light sheet microscopy (1). I am confused by the explanation of ...
1
vote
3answers
72 views

Derviation of group velocity

I am working thru a derivation of the group velocity formula and I get to this stage: $$y=2A\cos(x\frac{\Delta K}{2} -t\frac{\Delta \omega}{2})\sin( \bar k x-\bar \omega t)$$ Then all the derivations ...
1
vote
1answer
36 views

Intensity of Sound Wave

Is the intensity of a sound wave same at all the points through which the wave travels? The formula for intensity is $ I = \frac{{p_0}^2 }{2 \rho v}$. But this does not make sense to me. Shouldn't the ...
1
vote
1answer
192 views

Spherical wave amplitude near to source

Let us assume, I generate spherical waves from a point source, of the form $f(t)=\sin(t)$. At $r$ distance, it will be $\sin(t)/r$. Let us take $r = 0.1$ for example. Then, at this distance, the ...