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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“X-rays”, “gamma rays”, “sun rays”… But electromagnetic waves are NOT rays and DO NOT consist of rays?

In a separate question I'm struggling to figure out the nature of EM waves. But it's a vast topic and I'm trying to narrow it down to small specific questions. It turns out that all electromagnetic ...
0
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1answer
63 views

Is the wobbly rope depiction of a radio wave inherently wrong? And how do vectors of parallel waves align with each other?

I don't have a scientific education, yet I'm scientifically curious. Among other things, I'm struggling to understand the nature of electromagnetic waves. What I have recently realized is that the ...
2
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1answer
46 views

Question about standing wave

By considering the superposition of two waves propagating through a string, one representing the original or incident wave and the other representing the wave reflected at the fixed end, if both ends ...
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1answer
49 views

What's the difference between wave equation in PDE form and wave equation in normal form?

What's the difference between "wave equation in partial derivative form" and "wave equation in y(x,t) form" ? Are they both same? And why "wave equation in in y(x,t) form" is the solution of "wave ...
2
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1answer
71 views

How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model

I understand longitudinal waves. For example, I've got a clear mental modal of air waves: a slice of air becomes overcompressed, then the slice next to it becomes overcompressed and the first slice ...
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0answers
23 views

Traveling wave on a (transmission line) rope encountering a mass [on hold]

I would like to know the solution to this problem (or at least some very helpful tips): On a rope with a constant line density $\rho$ we have a traveling wave with wavelength lambda. On a certain ...
-1
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0answers
14 views

Reflected wave from free end

A wave pulse on a string moving from left to right towards a free end will reflect and propagates from right to left with the same speed and amplitude as the incident wave, and with the same polarity. ...
-2
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0answers
66 views

Understanding sine waveform [on hold]

I want to study the basics of propagating a periodic signal, i.e. sine waveform, which is a power signal. Let us consider an alternating current and write its expression as $$I(t) = I_m \sin(2\pi f ...
4
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0answers
69 views

The logarithmic decay of WIFI

I have been told that Wi-Fi, LTE etc signal strength fall of as $$\propto \frac1{\log(r)}$$ where $r$ is the distance. I am wondering why this is. I better explain what I mean with this question. ...
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2answers
39 views

How do we know the boundaries of a wavelength?

So the length of a wave is the distance between two compressed regions as shown in this representation of a longitudinal wave: But how do you know exactly where the two points are? Is there a point ...
1
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1answer
32 views

Question about force in transverse waves on a string

In deriving wave equation or power transmission of wave transmitted by a string, it is usually stated (with some assumptions) that the transverse force on a point of the string is proportional to the ...
1
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2answers
64 views

Physical meaning of wavelength of a EM Wave

The wavelength of a wave is defined as the spatial separation after which it repeats its shape. It is easy to visualize it for one dimension but if we consider a light wave/EM wave which is ...
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0answers
19 views

Minima of Single Slit Diffraction

In a single slit diffraction, it is approximated for the slit to compose of two slits of length $$ \frac{d}{2} $$ and hence the conditions for minima satisfy $$ \frac{d}{2}sin(\theta )= (n+ ...
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0answers
23 views

Energy distribution for a monochromatic plane wave [closed]

the task it to examine the energy distribution over the spectral components of a monochromatic plane wave averaged over time. To do this, I need to prove: There are no other clues! How do I ...
0
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1answer
47 views

Property of the wave functions of a free particle

How can I show that the following holds? $$\langle nlm\mid \partial_z^2\mid nlm\rangle=-\int_0^{4\pi}d\Omega\int_0^{\infty}drr^2\left|\partial_z\psi_{nlm}\right|^2$$ The wave functions of a free ...
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2answers
23 views

Propagation of transverse wave energy

Since I feel this question was not clearly answered, I am rewording it here. How does energy reaches from left to right in a transverse wave when the vibration of particles is only in "up and down" ...
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0answers
10 views

shear wave speeds and elastic anistropy

Background: I am working with 2d tissue slices that are known to be elastically anisotropic as a result of different collagen fiber bundle orientations. Question: I am interested in whether it is ...
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0answers
18 views

Propagation of force thought experiment [duplicate]

Imagine you have a million rigid spheres lined up edge to edge in a way that they can only move in one direction. now imagine that there is a wall at one end of this alignment. If you were to push at ...
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2answers
393 views

Sonic boom and resonance

Can the damage caused by sonic booms be seen as an example of resonance? that is, when the driving frequency (be the sound wave) is equal to the natural frequency of the glass being damaged?
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0answers
8 views

EM wave - phase change - amplitude [duplicate]

A plane electromagnetic wave has the shape: $\vec{E}(\vec{r},t)=E_0\cdot cos(\vec{k}\vec{r}-\omega t)\cdot \vec{e}_y$ $\vec{B}(\vec{r},t)=(B_1\cdot cos(\vec{k}\vec{r}-\omega t)+B_2\cdot ...
0
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2answers
42 views

A plane electromagnetic wave - phase change - amplitude

A plane electromagnetic wave has the shape: $\vec{E}(\vec{r},t)=E_0\cdot cos(\vec{k}\vec{r}-\omega t)\cdot \vec{e}_y$ $\vec{B}(\vec{r},t)=(B_1\cdot cos(\vec{k}\vec{r}-\omega t)+B_2\cdot ...
0
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1answer
88 views

Why is wave energy zero at maximum deviation?

The equation for the energy density of a longitudinal wave in a thin rod is $$w = \rho\cdot \left(\frac{\partial \xi}{\partial t}\right)^2$$ So the energy density seems to be 0 when the deviation ...
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1answer
48 views

Deriving basic form of sine wave [closed]

I'm trying to derive the basic form of a sine wave: $$y = A\sin(wt + θ)$$ I'm guessing I could probably first derive the cosine wave as follows and then add a phase of $- π/2$. $$y = Re(z) = ...
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1answer
27 views

relation between potential energy, kinetic energy and sound energy of water

When water flows its PE gets converted into KE so what causes its KE to get converted into sound energy and what the difference will occur in its sound if it is provided with a parallel surface?
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0answers
16 views

Models for vibrations and stress waves generated due to impact?

Say that a small metal ball impacts a long thin cylindrical rod from above (let's say height of around 10 cm) in an elastic collision and causes stress waves to propagate left and right from the point ...
0
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1answer
78 views

Waves speed and particle speed

Is the speed of a wave the same as the speed of the particle it displaces? Homework question,any help is appreciated.
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1answer
35 views

How sound waves are graphed

I asked a basic question about sounds waves recently and got really helpful answers. I have another question (from the same youtube video) about how different sound graphs are used in real world ...
0
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1answer
67 views

Can electrons reflect light?

Lately, I have been watching sparks while connecting my electronic devices and I can notice that electricity is kind of blue, and theoretically it's blue because it reflects blue wavelengths?? And ...
0
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1answer
43 views

Determining wave vector

If I have an $\mathbf{E}$ field: $$ \mathbf{E}_1 = (\hat x 2e^{j\pi/2} + \hat y5)e^{-j4z} $$ How do I find the wave vector $\vec{k}$? If I multiply through I get $ \mathbf{E}_1 = \hat x ...
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1answer
41 views

Using the equations $y(x,t)=A\sin(kx-wt)$ and $w=2\pi f$, if we solve for amplitude could we determine a relationship between amplitude and frequency?

I'm reading all over the internet that there is no relationship between frequency and amplitude of a wave given the context of a simple experiment where a string is tied between two points and one of ...
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0answers
27 views

Impact Force/Pressure of a wave on a vertical wall given PIV velocity field

I have PIV (Particle Image Velocimetry) data of liquid sloshing on a rectangular tank which produces a wave impacting one of the vertical walls. In the picture below you can see the wave about to hit ...
0
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0answers
16 views

How does a hologram record the incident laser?

How does the hologram (the photographic plate) record the incident laser beams when they hit onto it, what happens inside the hologram so that it records these laser beams?
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2answers
67 views

Why do water ripples widen (in plain English)

In this YouTube video water ripples start out with a wavelength of, say, 10 cm at the outer edge and they end up with a wavelength of about 30-40 cm towards the end of the video. Why does this happen, ...
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3answers
433 views

Do particles in a sound wave ever move vertically?

I'm trying to visualize how sound waves work and I was curious about something. So sound moves in longitudinal waves, which I think I understand. There is a really good khanacademy video explaining ...
0
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1answer
46 views

Observer carries beam of light and travels at speed of light

I am more of an "arm-chair" quantum physicists, i.e. I'm interested in books and articles about the subject. In the book "Tao of Physics" (Fritoj Capra) it mentions that when Einstein was 16, he ...
2
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2answers
280 views

Sound source not in a straight line with the sound receiver - does that make a difference?

Hope the graphics will help me explaining my question better. Let's say the box would be a room in the fourth floor, and the sound source would come from cars in the street. It is clear that in ...
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0answers
22 views

Relationship between phase velocity and group velocity with De Broglie postulates

If I have to show that the group velocity of a free particle is twice the phase velocity, is the following argument correct (avoiding to use the wave function and the momentum operator): For a ...
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1answer
25 views

What wavelength of light is the term 'focal length' defined against? [closed]

Because different wavelengths of light are bent differently in a medium, the focal length ought to be different for each of them (which is why white light splits up into a rainbow). If I have a "25 mm ...
2
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1answer
50 views

If EM waves are not physical, positional waves (on a X,Y,Z axis), why does interference pattern appear positional?

I have read that EM waves propagate in straight lines: https://van.physics.illinois.edu/qa/listing.php?id=17699 Wherein the only the electric (E) and magnetic (B) fields to change (or oscillate) at ...
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0answers
28 views

EM wave frequency vs. attenuation

Why does increasing frequency of an EM wave (for example in sea water with positive and negative ions floating about) increase the attenuation of the wave? Is the relative permittivity changed or the ...
0
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2answers
36 views

What is the least count of the timer clocks used in RADAR?

I was checking out some videos in YouTube regarding the working principle of RADAR. To quote some HOW IT WORKS: World War II Radar (720p), part 1, How does RADAR work? | James May Q&A | Head ...
2
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1answer
418 views

If a microwave oven disk rotates to warm up food, why doesn't it go up/down/sideways?

This has been in my mind for a while... Well, actually everytime I heat any food with a greater amount of liquid in it: a microwave oven warms up food by inducing polar molecules in the food to ...
4
votes
1answer
50 views

What, if anything, makes primary colours distinct?

I've recently become interested in the primary colours; red, green and blue. In my capacity as a computer programmer I'm well aware of how these colours are used practically, and of how varying ...
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0answers
24 views

visualization of Radar waves [closed]

I'm fairly interested in broadening my understanding of Radar waves due to my interest in modern air warfare in which radars play a very central role. How would radar waves appear visually if they ...
52
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3answers
8k views

Why doesn't the motion of a car affect the frequency of radio stations?

When we go in a car and tune to an FM radio station, why doesn't our motion disturb the frequency? Like the Doppler effect?
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27 views

How does the wavefront of sound or any other type of longitudinal waves look like?

In reality there is no crest on a longitudinal wave, even though compression is basically crest. So on this basis, there is really no visible wavefront. Is this true?
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2answers
45 views

Huygens' wave theory

The wave theory says that every point on the wavefront is taken as a source of secondary spherical wavelets. Now what I want to know is what does this actually mean? As every point is producing waves ...
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1answer
25 views

Molecular orbital theory

What I have learnt : When two waves overlap in phase, the resultant wave formed had a greater amplitude than that of the two interfering waves. When they overlap out of phase then the resultant ...
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1answer
31 views

EM waves in conductors

On a recent test in my E&M class, we derived what happens to an EM wave propogating in a conductor of conductivity $\sigma$, but I'm having trouble understanding the results. We started from the ...
3
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3answers
83 views

Materials that change their natural frequency

Say I have some material (solid, liquid, plasma, etc.). It has a set of natural frequencies. Now I pass a wave through it (sound, light, etc.). Once I pass the wave thought it, the material has a ...