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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Why do prisms work (why is refraction frequency dependent)?

It is well known that a prism can "split light" by separating different frequencies of light: Many sources state that the reason this happens is that the index of refraction is different for ...
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4answers
2k 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 ...
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12answers
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What happens to the energy when waves perfectly cancel each other?

What happens to the energy when waves perfectly cancel each other (destructive interference)? It appears that the energy "disappear" but the law of conservation of energy states that it can't be ...
23
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5answers
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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 ...
24
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4answers
9k views

Amplitude of an electromagnetic wave containing a single photon

Given a light pulse in vacuum containing a single photon with an energy $E=h\nu$, what is the peak value of the electric / magnetic field?
4
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2answers
5k views

Group Velocity and Phase Velocity of Matter Wave?

In quantum mechanics, what is the difference between group velocity and phase velocity of matter wave? How can it also be that phase velocity of matter wave always exceeds the speed of light?
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5answers
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Radio antenna producing waves in the visible spectrum [closed]

If a radio could produce waves in the visible light spectrum, what would the result be? This is a thought experiment that I've pondered for a few years now. I realize there are a few/many real-world ...
289
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4answers
43k views

Can I compute the mass of a coin based on the sound of its fall?

Other day, I bumped my bookshelf and a coin fell down. This gave me an idea. Is it possible to compute the mass of a coin, based on the sound emitted when it falls? I think that there should be a ...
5
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2answers
7k 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. ...
9
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4answers
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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 ...
7
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2answers
3k views

How do mirrors work?

My physics professor explained to me that electromagnetic waves are consisted of two components - electric and magnetic - which cause each other. Which part of the mirror actually reflects the wave? ...
2
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2answers
444 views

What restrictions on time boundary conditions does it have to use Fourier transform to solve wave equation?

The wave equation can be solved using Fourier transform, by assuming a solution of the form of $$\mathbf{E}(x,y,z,t)~=~\mathbf{E}(x,y,z)e^{j\omega t}$$ and then reducing the equation to the Helmholtz ...
7
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2answers
490 views

Patterns in laminar flow of tap water

This is a simple experiment that anyone can do at home. Open your tap so that the water maintains a laminar flow, and the cross section of flow is considerably thin. Place your finger 3-4 cm below the ...
3
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2answers
507 views

Why do light disappears the moment we switch off the source (inside the wooden box)?

I am failing to explain why light won't remain inside the wooden box in the following situation. I considered a wooden box closed from all the sides, with a bulb inside it. If we switch on the bulb, ...
6
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4answers
237 views

Is light amplitude spatial?

In diagrams I often see light waves depicted as little sine waves that travel through space. And often when describing polarizers, the explainer will angle their hand to show the angle of ...
9
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2answers
1k views

If light rays obey to the wave equation, why can they be thought as straight lines?

I'm a newbie with physics but I'm wondering how a ray of light can essentially be represented. I have always known that a ray of light proceeds in a straight line until it encounters another object ...
10
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4answers
2k views

What does a de Broglie wave look like?

What does a de Broglie wave look like? Are de Broglie waves transverse or longitudinal? Can they be polarized? What about the de Broglie wave of a ground state neutral spin-zero Helium 4 atom? ...
4
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2answers
7k 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 ...
5
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4answers
1k views

Optical explanation of images of stars?

Very often when viewing pictures of the cosmos taken by telescopes, one can observe that larger/brighter stars do not appear precisely as points/circles on the image. Indeed, the brighter the light ...
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4answers
2k views

Popular depictions of electromagnetic wave: is there an error?

Here are some depictions of electromagnetic wave, similar to the depictions in other places: Isn't there an error? It is logical to presume that the electric field should have maximum when ...
16
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5answers
3k views

Do the electric and magnetic components of an electromagnetic wave really generate each other?

Frequently when EM waves are taught, it is said that the change in electric field causes a change in the magnetic field, which then causes a change in the electric field, and so on and so forth. But ...
11
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7answers
2k views

Why don't waves erase out each other when looking onto a wall?

If I stand exactly in front of a colorful wall, I imagine the light waves they emit, and they receive should randomly double or erase out each other. So as a result, I imagine I should see a weird ...
3
votes
2answers
19k views

How is the speed of light calculated?

How is the speed of light calculated? My knowledge of physics is limited to how much I studied till high school. One way that comes to my mind is: if we throw light from one point to another (of known ...
13
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1answer
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Theory behind patterns formed on Chladni plates?

In this video of vibrating Chladni plates we can see small sand particles align themselves into different interesting patterns (also shown in the image below) which correspond to some particular ...
6
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3answers
851 views

Recently publicized experiment on destructive interference between two laser beams

Recently I've had several non-physicist friends ask me, independently of each other, about an experiment where two collinear laser beams destructively interfere along a certain length. Everybody wants ...
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2answers
10k views

Frequency of the sound when blowing in a bottle

I'm sure you have tried sometime to make a sound by blowing in an empty bottle. Of course, the tone/frequency of the sound modifies if the bottle changes its shape, volume, etc. I am interested in ...
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2answers
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The shape of speaker cones

This is related to another question I just asked, but they are different enough I thought it deserved its own spot. Speaker elements seem to always be shaped like a cone with a portion of a sphere at ...
4
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2answers
741 views

Do Photons Move in a Wave Like Pattern? [duplicate]

In many pieces of literature, light is said to travel like a "wave". Does this mean the light literally propagates through space like a wave as in up and down and so on or does light move linearly ...
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5answers
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Waves in water always circular

I have had a question since childhood. Why do we always get circular waves (ripples) in water even when we throw irregularly shaped object in it?
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9answers
5k views

Why do we think of light as a wave?

I've read that light travels in a straight line and has a wavelength of 400nm to 700nm. But I don't understand why does it have a wavelength and what creates its wavelength? I agree with the concept ...
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3answers
252 views

How are gravitational waves exactly produced?

I was thinking about gravitational waves, and I found out that I may have a doubt about their production. Assuming the whole calculations find a wave-like solution to be understood, I was wondering ...
0
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2answers
278 views

Uncertainty and wave-trains

My textbook and the following extract from feynman's lectures present the same idea regarding wavetrains and uncertainty in their wavelengths. Why is it that a wavetrain confined to some space has an ...
18
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8answers
3k views

Why are sine/cosine always used to describe oscillations?

What I am really asking is are there other functions that, like $\sin()$ and $\cos()$ are bounded from above and below, and periodic? If there are, why are they never used to describe oscillations in ...
17
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4answers
4k views

Energy conservation and interference

I have a problem with energy conservation in case of interfering waves. Imagine two harmonic waves with amplitudes $A$. They both carry energy that is proportional to $A^2$, so the total energy is ...
16
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6answers
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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 ...
8
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2answers
8k 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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5answers
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Producing photons with same frequency, different amplitude wave [duplicate]

I don't understand how two photons of the same frequency can have different amplitudes, neither how to produce them. I know that classically the square of the amplitude is proportional to the energy, ...
5
votes
2answers
3k views

What Exactly is a Shock Wave?

The Wikipedia defintion of a shock wave pretty much sums up all I've found online about what a shock wave is: A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries ...
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3answers
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Prove EM Waves Are Transverse In Nature

Why we say that EM waves are transverse in nature? I have seen some proofs regarding my question but they all calculate flux through imaginary cube. Here is My REAL problem that I can't here imagine ...
19
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1answer
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How can shock waves travel faster than sound?

A shock wave can be caused by the disturbance of air by an airplane. When it propagates, shouldn't the mechanism be the same as that of a longitudinal sound wave? Why can a shock travel faster than ...
14
votes
4answers
2k views

Can light waves cause beats?

My question is pretty brief. When two sound waves of nearly same frequencies interfere, we get beats. But, I have not observed something like that happening in the case of light. In fact, most of the ...
12
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2answers
1k views

How is the Schroedinger equation a wave equation?

Wave equations take the form: $$\frac{ \partial^2 f} {\partial t^2} = c^2 \nabla ^2f$$ But the Schroedinger equation takes the form: $$i \hbar \frac{ \partial f} {\partial t} = - \frac{\hbar ...
7
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1answer
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Phase and Group Velocity of Electromagnetic Waves

Moving charges produce oscillating electric and magnetic fields -we have an electromagnetic wave. In terms of moving charges or at the level of charges, what is phase velocity and group velocity of ...
4
votes
3answers
522 views

Double-Slit Experiment Separation Between Fringes

I was taught in class that the double slit diffraction pattern would always have bright fringes of same length. We derived the formula: $y=m(\lambda)(L)/d$, which also shows this equal distance. I ...
4
votes
2answers
4k views

The energy of an electromagnetic wave

The intensity of an electromagnetic wave is only related to its amplitude $E^2$ and not its frequency. A photon has the same wavelength as the wave that's carrying it, and its energy is $h f$. So ...
3
votes
2answers
255 views

How does Huygens Principle incorporate the unidirectional property of a traveling wave?

I was reading French's Vibrations & Waves where he discusses Huygens-Frensel Principle. The principle talks about how secondary sources give rise to secondary wavelets to form the displaced ...
3
votes
1answer
223 views

How to create a barrier for sound waves?

Is there a way to create a barrier so that sound waves cannot pass through? Does laser light have this ability to act as a barrier or bounce sound waves back? This came to my mind when I was ...
2
votes
1answer
279 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 ...
2
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1answer
641 views

Diffracton at the edges of an opaque object?

To understand the phenomenon of diffraction as an interference effects of several dipole oscillators (like in case of several symmetrical, not sawtooth, scratches in a diffraction grating), we ...
2
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1answer
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How to calculate the intensity of the interference of two waves in a given point? [closed]

There are two different point sources which produce spherical waves with the same power, amplitude, ω, wavenumber and phase. I can calculate the intensity of each wave in a point: $$ I_1 = P / (4 ...