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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Counting the modes of the vector potential in a coulomb gauge
With a view to quantising the EM field, consider a classical free field in the absence of charge and currents, we can take a coulomb gauge, $\phi=0, \partial_kA_k=0$. The physical fields in terms of ...
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134 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 ...
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1answer
70 views
Standing Waves: finding the number of antinodes
A string with a fixed frequency vibrator at one end forms a standing wave with 4 antinodes when under tension T1. When the tension is slowly increased, the standing wave disappears until tension T2 is ...
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46 views
Boundary conditions on wave equation
I am having trouble understanding the boundary conditions.
From the solutions, the first is that $D_1(0, t) = D_2(0, t)$ because the rope can't break at the junction.
The second is that ...
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35 views
Standing Waves in Flutes
How do the waves produced in flutes have a wave characteristic while maintaining a velocity that allows them to travel to out ear? If it were simply a standing wave I'd imagine that they would ...
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1answer
41 views
How large of a solar sail would be needed to travel to mars in under a year?
I'm attempting to approach this using the identity
$$F/A = I/c$$
I can solve for Area easily enough
$$A = F(c/I)$$
and I know the distance $d$ is
$$d=1/2(at^2)$$
But I'm having difficulty trying to ...
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1answer
28 views
Relation of color and frequency for the visible spectrum
In this question the OP is looking for a way to see light that is outside of the visible spectrum without using electronic sensors. This got me wondering about the visible spectrum itself. Typically ...
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1answer
53 views
The second resonance of string?
What is the relationship between "the second resonance " and string and the wavelength. Like in this question: if the length of the string is 2cm with second resonance, then what is wavelength?
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1answer
62 views
Phase shift of resonance
For resonance to occur, is it true that the force lags behind the motion by $\pi/2$? I saw some notes written that the motion lags behind the force by $\pi/2$ which makes no sense to me.
As I watched ...
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3answers
71 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 ...
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1answer
77 views
Why do sound waves travel at the same speed moleculewise? (Same medium)
I don't understand what happens in reality (outside of wave theories). If I clap my hands I invest energy in the nearby air molecules, which move and transfer their energy to nearby molecules which ...
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1answer
80 views
Critical bathymetric profile to maximize surge and minimize breaking?
Reading about storm surge, I found it fascinating that the gradual slope of the Gulf Coast of Florida resulted in a much higher storm surge but much lower energy release in breaking waves.
Is there ...
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1answer
52 views
Will changing amplitude change the frequency?
Will changing the amplitude change the frequency of a wave, or is it possible for a specific frequency (50 Hz. for example) to generate from shifting amplitude patterns?
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2answers
81 views
Is there a way to create a flickering frequency to be dependent on speed of the person looking at it?
Is there a way to make a screen or a road sign flash at different rates, depending on the velocity of the observer looking at it?
I would like to achieve a state where two observers going at ...
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0answers
61 views
Slinky reverb: the origin of the iconic Star Wars blaster sound
This is a fun problem that I came across recently, which I'm posting here for your delectation. We all love a good slinky: they can be used for all sorts of fun demos in physics. One example is the ...
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13 views
Minimum thickness of bubble ensuring max reflectance
A soap bubble has index of refraction of 1.33. What minimum thickness of this bubble will ensure max reflectance of normally incident 530 nm light?
Ans is 99.6, but how do I get that?
I am ...
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3answers
2k views
Phase shift of 180 degrees on reflection from optically denser medium
Can anyone please provide an intuitive explanation of why phase shift of 180 degrees occurs in the Electric Field of a EM wave,when reflected from an optically denser medium?
I tried searching for it ...
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1answer
27 views
Phasor representation of voltage in frequency domain
In a text on application of electromagnetism in transmission line, there introduces a phasor for the voltage (in frequency domain)
$$\tilde{V}(x) = V^+e^{-i\beta x} + V^-e^{i\beta x.}$$
Here $V^+$ ...
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3answers
74 views
Lethality of sounds and extreme “loudness”
In theory, could pure sound be lethal? How loud would it have to be? Also, which events are the loudest in the universe, and how loud are they? I'm confining attention to events which occur regularly, ...
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1answer
45 views
EM Waves Energy Loss
Where does the energy go when two photons interfere destructively at a point on a screen in Young's double slit experiment ?
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Implementing Explicit formulation of 1D wave equation in Matlab #FiniteElements #FiniteDifferences [migrated]
so the theory is straight forward.
we have:
$\frac{d^2U}{(\Delta t)^2}=c^2 \frac{d^2U}{(\Delta x)^2}$
discretizing it gives:
$\frac{U(i+1,j)- 2U(i,j) + U(i-1,j)}{(\Delta t)^2} = c^2 ...
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1answer
112 views
Eddy current losses in electric steel by harmonics of a magnetic field
I am working on an model of a permanent magnet synchronous machine. Right now I am stuck with calculating the eddy current losses caused by the harmonics of the stator magnetic field in the electrical ...
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44 views
Longitudinal EMAG wave?
I'm reading about optical waveguide analysis, and often come across the terms "transverse electric mode" vs. "transverse magnetic mode". As I unerstand, it means that the electric/magnetic field has ...
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2answers
137 views
Standing Waves Energy transfer
And In a standing wave , how does energy travel past a node in a string ?
It should just get reflected . Assume the case of first overtone and you strike the string at a place . How will energy ...
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2answers
139 views
De Broglie wavelength, frequency and velocity - interpretation
Two fundamental equations regarding wave-particle duality are:
$$ \lambda = \frac{h}{p},
\\
\nu = E/h .$$
We talk about de Broglie wavelength, is it meaningful to talk about de Broglie frequency ...
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1answer
216 views
De broglie equation
What is the de Broglie wavelength?
Also, does the $\lambda$ sign in the de Broglie equation stand for the normal wavelength or the de Broglie wavelength? If $\lambda$ is the normal wavelength of a ...
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5answers
967 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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1answer
289 views
Ultrasonic wave through air
I am not a physicist but I am extremely interested in this area.
The simple version of my question is:
"What is the maximum range of an ultrasonic wave traveling through air?"
Now, I know it depends ...
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0answers
56 views
Double Slit Problem Involving Superposition of Wave Equation [closed]
Here's my question:
To be clear it's part (iv) that's unclear to me.
I can see that the important bit is that the exposure is over a LONG time. Hence, this must have some implication on the manner ...
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1answer
64 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 ...
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2answers
168 views
Counting electromagnetic modes in a rectangular cavity and boundary conditions
The electric field in a cubical cavity of side length $L$ with perfectly conducting walls is
$E_x = E_1 \cos(n_1 x \pi/L) \sin(n_2 y \pi/L) \sin(n_3 z \pi/L) \sin(\omega t)$
$E_y = E_2 \sin(n_1 x ...
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1answer
29 views
Why frequency and tension doesn't change in the two medium?
I am reading a book about wave mechanics. There are two different cord (one light and one heavy) connected together, one person waving the lighter one, the wave transverse to the right from the ...
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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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3answers
108 views
Waveguides (in the ocean?)
The speed of sound in the ocean is given by
$$c_s(\theta,z) = 1450 + 4.6\theta - 0.055\theta^2 + 0.016z$$
$\theta$ is the temperature in degrees celcius, and $z$ is the depth. In a simplified model, ...
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0answers
46 views
Fourier Transform of ribbon's beam Electric Field
I have a monochromatic ribbon beam with $E(x)e^{i(kz-\omega t)}$ being the electric field's amplitude. I want to show that the lowest order approximation in terms of plane waves is
...
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2answers
81 views
In terms of the Doppler effect, what happens when the source is moving faster than the wave?
I'm just trying to understand this problem from a qualitative perspective. The Doppler effect is commonly explained in terms of how a siren sounds higher in pitch as it is approaching a particular ...
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50 views
Could anyone help me to interpret the wave geometrically? [closed]
This is the problem:
A 180-MHz wave travels in medium characterized by $\mu_r = 1$, $\epsilon_r = 25$, and $\sigma = 2.5$ mS/m. The electric field intensity is given by $\widetilde{E} = ...
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1answer
36 views
Nodes and Antinodes for standing wave
In the arrangement shown in the figure below, an object of mass m can
be hung from a string (linear mass density $\mu$ = 2.00 g/m) that passes over
a light (massless) pulley. The string is connected ...
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1answer
124 views
Relationship between gauss and decibels
In my ongoing effort to understand the world around me, I want to wrap my head around the relationships between two units of measure. Specifically gauss and decibels.
The quandary comes from my ...
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2answers
88 views
Calculating phase difference of sound waves
An observer stands 3 m from speaker A and 5 m from speaker B. Both speakers, oscillating in phase, produce waves with a frequency of 250 Hz. The speed of sound in air is 340 m/s. What is the phase ...
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1answer
50 views
Power radiated by the sun at different locations
I am wondering can someone help to solve second part which extends first part;
The power radiated by the sun is ${3.9*10^{26}}_{watt}$. The earth orbits the sun in a nearly circular orbit of radius ...
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1answer
72 views
Can you “fold” EM or light waves? (i.e) long wave that is reflected by mirror in fragments - like in the game “Snake”
So, I was reading about the Casimir effect. Two mirrors facing each other attract to each other in a vacuum. The reason is due to pressure exerted on those mirrors from the multitude of EM waves (like ...
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1answer
96 views
How does one find the wave velocity and the phase speed?
While I was studying beats, I tried to find a displacement function of any particle in the most generalized form. I ended up with $$y=2A\sin(\pi(t-x/v)(f_1+f_2))\cos(\pi(t-x/v)(f_1-f_2)).$$
Now, ...
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0answers
28 views
The interference of waves and factors that affect cancellation?
If you had two repeated disturbances on the surface of a water, I know interference will occur. However, if I move the two sources of disturbances closer together, why would the 'gaps' between each ...
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3answers
794 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 ...
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2answers
124 views
How to reproduce highway vibration?
I would like to test my hardware under vibration that can appear on a highway gantry.
If someone has a model of such vibration. i.e period and amplitude.
In my lab I have a motor that can be ...
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2answers
176 views
Are there “gaps” in light, or will it hit everywhere?
Not sure how to word my question.
Picture a light source in vacuum, so nothing disturbs the light (or similar conditions), 2d.
If I move very, very far away, will it happen that some of the light ...
3
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2answers
195 views
Can someone explain how water from a garden hose can propagate in a sine/cosine wave?
A video posted on Youtube : http://www.youtube.com/watch?feature=player_embedded&v=uENITui5_jU
How does this phenomenon work? I know he is using frequency to propagate water in a sine/cosine ...
3
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2answers
3k views
Do light and sound waves have mass
I have been reading Hawking's 'A Brief History of Time' and it has gotten me thinking about Einstein's theory of relativity, in that it assumes that an object must have infinite mass if it is to be ...
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3answers
229 views
Validity of naively computing the de Broglie wavelength of a macroscopic object
Many introductory quantum mechanics textbooks include simple exercises on computing the de Broglie wavelength of macroscopic objects, often contrasting the results with that of a proton, etc.
For ...
