Waves are disturbances that propagate throush 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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246 views
Angular frequency. Wrong interpretation at Wikipedia?
This and this articles mention that the angular frequency is:
number of oscillations per unit of time
But this doesn't seem to be correct since the angular ...
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1answer
342 views
How does a speaker produced different sounds?
What I have read is that a speaker produce sound by just moving a coil attached to a cone which moves back and forth. So, If I try to move the coil by hand, would it produce sound? If not why not? or ...
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3answers
451 views
Electromagnetic wave reflection vs. light reflection
Related: x-ray interaction with atmosphere
I know that electromagnetic waves of particular frequencies reflect from the ionosphere. And the light (which from one perspective is an electromagnetic ...
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1answer
165 views
Wave equation from hooke law - simple question
In the paragraph http://en.wikipedia.org/wiki/Wave_equation#From_Hooke.27s_law
it is said, regarding the u(x) function, that
Here u(x) measures the distance from the equilibrium of the mass
...
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2answers
180 views
Does EM radiation (any, i.e. RF), or sound, radiate everywhere at once?
I am having trouble understanding electromagnetic radiation (or waves in general, be it EM or sound). If I have a 1 Watt speaker, is it infinitely divided and spread out so that everyone in every ...
7
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3answers
815 views
Why is it necessary for an object to have a bigger size than the wavelength of light in order for us to see it?
I keep hearing this rule that an object must have a bigger size than the wavelength of light in order for us to see it, and though I don't have any professional relationship with physics, I want to ...
3
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2answers
342 views
Energy in an EM wave should depend on frequency
I just finished reading Feynman's Lectures on Physics vol.I, ยง34-9: "The momentum of light". The author explains that there is a relation between the wave 4-vector $k^{\mu}$ and the energy-momentum ...
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2answers
301 views
A simple question about the stationary wave and fundamental frequency
Suppose we have 2 fixed end connected with a wire and now we insert a vibrator in the middle of the wire, and resonance occur. How would the fundamental frequency looks like?
I know the case when the ...
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1answer
773 views
Relation between wavenumber and propagation constant
What is the exact difference between wavenumber and propagation constant in an electromagnetic wave propagating in a medium such as a transmission line, cause i am a bit confused. Does it have to do ...
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1answer
72 views
Close electric field lines in wave guides
In a wave guide, graphics of propagation of Transversal Magnetic modes show closed field lines for the electric field.
For example, for a rectangular guide:
$E_x (x,y,z) = \frac {-j\beta m \pi}{a ...
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1answer
67 views
How does one determine whether an object will make an EM wave refract in a qualitative way?
for example, i have a vague notion that the actual answer is that the permittivity and permisivity are different in each different material, so all waves refract at every boundary, but we only call it ...
2
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1answer
159 views
Confusion concerning the use of wavenumber in exercise about Fabry-Perot etalon
In the exercise we are given that the spectrum of a light source consists of two spectral lines, which both have wavelengths around $500 \text{ nm}$ and the separation between them - given in ...
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0answers
172 views
How to predict sea waves length/height?
I would like to know which are the best methods used to predict sea waves characteristics (particularly predict length/height given water depth and wind speed) and how are they used. My major is ...
2
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1answer
212 views
Counting the number of modes
The exercise is the following
Show that the number $N(\lambda) \, \mathrm d \lambda$ of standing electromagnetic waves (modes) in a large cube of volume $V$ with wavelengts within the interval ...
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2answers
318 views
Why is Polarization of a wave important, and what happens when a wave is polarized in all three dimensions?
I don't quite understand this, I understand that given a wave traveling in a certain direction, it will be polarized in the direction its not travelling in, so if its travelling in the Z direction, k ...
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3answers
2k views
Why do bass tones travel through walls?
I was in the shower while my roommate was listening to music and got to thinking about the fact that I could only hear the bass and lower drums through the walls. Why is this? The two possibilities I ...
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1answer
228 views
How much energy is contained in a 40 meter wave?
Consider a wave that stands 40 meters high in the sea on very deep water. How much energy would approximately be contained in this wave if it was 100 meters wide and had been produced by wind?
Is ...
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1answer
256 views
Speed of Light, Photons or WaveSpeed?
The speed of light is almost 300 000 km/s.
The photons have a speed along the wave, and the wave have a speed straight forwards.
What is the speed of light? Is it the speed the photons have along ...
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3answers
209 views
Testing my understanding of QM - The Double Slit Experiment without the slit
First off, sorry to throw in another question from someone who hasn't studied the maths.
I'd like to see if I have a correct (if very basic and non-mathematical) understanding of the wave and ...
3
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2answers
899 views
why is mechanical waves faster in denser medium while EM waves slower?
Why is it that mechanical waves/longitudinal waves/sound travel faster in a denser/stiffer medium as in steel compared to say air, while EM waves/trasverse waves/light travels slower in a (optically) ...
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4answers
1k views
How can a sine wave represent a longitudinal wave?
I envision a longitudinal wave as a series of vertical lines like that drawn on the board in an introductory physics class. This image contains no angles. Sound is a longitudinal wave.
Some ...
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2answers
160 views
Radar Frequency Bandwidth
I've come across an interesting question in the course of doing some exam review in a quantum mechanics book and thought I'd share it here.
"What must be the frequency bandwidth of the detecting and ...
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3answers
398 views
Sine wave, $\pi$ and frequency
Please explain the relation $\sin(2\pi ft)$ such that how the $\pi$ (which is actually circumference/diameter of a circle) relates with the sine wave which is having a longitudinal vibration?
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2answers
176 views
Does a finite wave necessarily have to be non-monochromatic in reality?
Does a finite wave necessarily have to be non-monochromatic in reality, or is that implication just a result of the mathematical analysis? I always wonder at these sort of things that come out of a ...
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1answer
204 views
Transparent boundary condition. Beam propagation method
I am interested in the finite-difference beam propagation method and its applications. I try to solve the Helmholtz equation. At first, i would like to solve numerically it for the easiest case, ...
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3answers
2k views
Why is energy in a wave proportional to amplitude squared
I'm a mathematics student trying to grasp some basics about wave propagation. A sentence I find very often in introductive physics textbooks is the following:
In a wave, energy is proportional to ...
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1answer
188 views
1D Wave mechanics (string)
Suppose I have a wave traveling to the right described by $e^{iw(t-{x\over c})}$. (It obeys the 1D wave equation). AND at $x=0$, there is a mass $M$ fixed to the string such that we have $M{d^2y\over ...
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2answers
792 views
Speed of a particle in quantum mechanics: phase velocity vs. group velocity
Given that one usually defines two different velocities for a wave, these being the phase velocity and the group velocity, I was asking their meaning for the associated particle in quantum mechanics.
...
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2answers
153 views
How do the LASERs in LIGO realize that space has expanded as a gravitational wave passes by?
I read an article on LIGO, and I heard it mentioned that it is a nontrivial argument to say that the effect can be measured by interferometry. What happens to space as the wave passes? Does the light ...
2
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3answers
898 views
What's a good textbook to learn about waves and oscillations?
I'm taking a course on waves and oscillations using Crawford from the Berkeley series (out of print excluding international copies), and would like to know if anyone has any suggestions for a better ...
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5answers
975 views
How to Make RF Waves Visible
I understand RF (Radio Frequency) Waves are electromagnetic waves and a mode of communication for wireless technologies, such as cordless phones, radar, ham radio, GPS, and television broadcasts. Most ...
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2answers
798 views
Why does Davisson-Germer experiment confirm electron's wave-particle duality?
First I apologize if my question is trivial and for my poor English.
I was wondering why my teacher states that "electron's wave-particle duality is verified if we observe diffraction of the electron ...
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2answers
238 views
What is a wave?
I was watching an outtake of Prof. Brian Cox talking to a tv producer about "gravity waves". Their discussion got a bit side-tracked, because the non-scientist didn't seem to understand what a wave ...
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1answer
308 views
Why do I hear beats through headphones only at low frequencies?
I was recently playing with this Wolfram Demonstrations applet, which demonstrates beats.
At first I thought the app didn't work because I couldn't hear any beats. Then I realized that the applet ...
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2answers
350 views
Does space have to be filled with charged particles to carry electromagnetic waves?
I'm a newbie here so have mercy.
I'm studying electromagnetic waves. This is the propagation of energy via the vibration of charged particles, as I understand it.
A charged particle could be like ...
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0answers
298 views
Hankel function in terms of planewaves [closed]
It is well know that planewaves are a complete basis for solutions to the wave equation. Let us assume a 2D space, and at fixed temporal frequency, the equation reduces to the Helmholtz equation. In ...
4
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2answers
302 views
Interference of EM Waves with Orbital Angular Momentum
If you have two coherent collinear e-m beams of same frequency and polarization, but 180 degrees out of phase, they will destructively interfere.
If you introduce orbital angular momentum of L=3 ...
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1answer
481 views
Changing magnetic flux graph?
In regards to a graph of the changing magnetic flux in a generator such as this one:
a) The equation of the graph should be $\Phi = BA \cos \theta$. As $\theta=\omega t$ (angular velocity*time), ...
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2answers
798 views
Wave / particle duality question for sound and light
Sound is usually referred to as just "sound waves" - we do not talk about a "sound particle" and only as a wave or "matter wave."
Could something similar apply to light i.e. that there really is no ...
3
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1answer
113 views
What is it that undulates in a particle?
When there is a wave, something is undulating. In the example of a rope, the rope is what undulates. In the case of a ripple on a pond, the water is undulating, and when a sound wave propagates, the ...
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1answer
128 views
How colored light can be explained if light is considered as emission of photon?
If light is considered as wave, then different colored light can be explained as waves of different wavelength/frequency. How colored light can be explained if light is considered as emission of ...
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0answers
234 views
Depth of sea and point at which waves break
Following up on this answer, is the point at which waves break on the sea shore a guide to the depth of the sea at that point? Could it indicate eg hidden rocks?
Explain the direction of waves on sea ...
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1answer
1k views
Explain the direction of waves on sea shore
Why do waves on the sea shore move towards the shore even when the tide is going out?
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0answers
118 views
Reflected electromagnetic wave relation
If incident electromagnetic wave is given as:
$$\begin{align*}E_i&=A_e \cos(\omega t + bz)\\
H_i&=A_h \cos(\omega t + bz)\end{align*}$$
What would be relation for REFLECTED wave?
Does it ...
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1answer
139 views
Spring oscillations and waves
Consider a block of mass $m$ attached to a spring. Let it oscillate at a frequency $f$. Now each part of the spring is in SHM. so this means a wave is propagating through this spring.bCan this wave be ...
6
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2answers
161 views
Multiple channels of information in single electromagnetic wave?
I'm trying to understand how can multiple radio stations transmit information just by transmitting using different frequency. The way I understand it all those different frequency waves add up to a ...
3
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2answers
210 views
Waveguide and ethernet
I am having a doubt about waveguides and the traditional Ethernet cable.
The newest Ethernet i.e. the 10Gbps Ethernet has an astounding speed of 10Gbps. Which consists of 4 lanes in Cu as physical ...
3
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1answer
240 views
Lorentz invariance of a frequency- and wavelength- dependent dielectric tensor
Suppose we have a material described by a dielectric tensor $\bar{\epsilon}$. In frequency domain, this tensor depends on the wave frequency $\omega$ and the wave vector $\vec{k}$.
Clearly not all ...
6
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1answer
303 views
The role of metric in the Wave Equation
The wave equation is often written in the form
$$(\partial^2_t-\Delta)u=0,$$
involving the Laplace-Beltrami operator $\Delta$. However, the Laplace-Beltrami operator $\Delta$ is defined only in the ...
2
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2answers
475 views
coherence length
Suppose i have two waves emanating from a point source. The waves start out completely in phase.
Is the coherence length consistently defined as the length at which these two waves achieve a phase ...
