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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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 ...
13
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4answers
8k 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 ...
35
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10answers
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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 ...
16
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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
1k views

How do mirrors work?

Apparently, light is just a certain wavelength, or "the visible spectrum" of electromagnetic waves. If I recall correctly, my physics teacher explained to me that electromagnetic waves are basically ...
10
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4answers
723 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 ...
2
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2answers
217 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 ...
3
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2answers
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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. ...
7
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4answers
5k 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 ...
8
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2answers
271 views

Is there a good chance that gravitational waves will be detected in the next years?

Is there a good chance that gravitational waves will be detected in the next years? Theoretical estimates on the size of the effect and the sensitivity of the newest detectors should permit a ...
3
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2answers
1k 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?
5
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4answers
835 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? ...
5
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4answers
681 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 ...
2
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2answers
2k 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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3answers
610 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 ...
3
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2answers
6k 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 ...
9
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6answers
1k 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 ...
9
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3answers
1k 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 ...
3
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2answers
1k views

How can sound waves propagate through air?

We know that the sound waves propagate through air, and it can't travel through vacuum. so the thing that help it doing that is the air's molecules pressure. So my question how can that happens? I ...
3
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2answers
5k 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 ...
7
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5answers
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Why aren't there compression waves in electromagnetic fields?

I just started learning about optics, and in the book I'm reading they explain how the electrical field caused by a single charged particle could be described by a series of field lines, and compare ...
2
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3answers
1k views

Producing photons with same frequency, different amplitude wave

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, ...
9
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2answers
303 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 ...
8
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3answers
596 views

Boundary layer theory in fluids learning resources

I'm trying to understand boundary layer theory in fluids. All I've found are dimensional arguments, order of magnitude arguments, etc... What I'm looking for is more mathematically sound arguments. ...
8
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4answers
2k views

Are water waves (i.e. on the surface of the ocean) longitudinal or transverse?

I'm convinced that water waves for example: are a combination of longitudinal and transverse. Any references or proofs of this or otherwise?
6
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2answers
409 views

Can someone explain how water from a garden hose can propagate in a sine/cosine wave?

A video posted on Youtube. How does this phenomenon work? I know he is using frequency to propagate water in a sine/cosine wave, but how does it exactly work this way? Why do we see it as if its ...
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10answers
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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 ...
3
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2answers
113 views

Diffraction by a lens

The fraunhoffer treatment of circular apertures yields a diffraction pattern of circles, with the first minimum (dark ring) at an angular radius of $\theta$ where $\sin(\theta)=1.22\lambda/b$, where ...
3
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1answer
125 views

More extensions of the wave equation for dispersion

The Phys.SE question Minimal Extension of Wave Equation to Include Dispersion extended the wave equation for only a very simple form of dispersion. However, what about more complex dispersion ...
3
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2answers
2k 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 ...
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2answers
68 views

Why doesn't the magnetic field polarize when polarizing light?

If the magnetic field doesn't polarize does it follow the electric field path of propagation? or does it vanish?
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4answers
320 views

Radio antenna producing waves in the visible spectrum

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 ...
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2answers
385 views

Refraction of light and frequency dependence

Why do higher frequency waves refract more, both ocean waves and light waves? Also why is energy stored in the frequency as opposed to the wavelength.
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1answer
2k views

Science behind the singing wine glass

A wine glass filled with water (approximately half or a quarter), when you use a wet finger and rub the top of the wine glass, the wine glass will produce a sound. I heard that it is because of the ...
0
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1answer
248 views

Deriving the group velocity of a wave produced by some basic cosine waves with unequal amplitudes

Consider some basic cosine waves of the form ${E_i} = {E_0}\cos ({\omega _i}t - {k_i}z)$ with different amplitudes, frequencies and phases. We know a combination of such waves could result in a wave ...
0
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1answer
86 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 ...
0
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1answer
244 views

Help me to visualize this wave equation in time, to which direction it moves?

The wave is $\bar{E} = E_{0} sin(\frac{2\pi z}{\lambda} + wt) \bar{i} + E_{0} cos(\frac{2 \pi z}{\lambda}+wt) \bar{j}$ Let's simplify with $z = 1$. Now the xy-axis is defined by parametrization ...
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4answers
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Electro Magnetic Waves can cause matter displacement?

After watching this video: http://www.youtube.com/watch?v=j1jIjx0XF_U The experience is made with a speaker that generates a sound wave or mechanic wave. Can you use this to establish a link to ...
7
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3answers
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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 ...
5
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2answers
183 views

Which solution to the electromagnetic wave equation is the most accurate model of monochromatic light?

When a photon is modeled as a monochromatic electromagnetic wave its electric and magnetic components are usually taken to be sine waves (for example here ...
10
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2answers
272 views

First-order wave equation: Why is its presence not common?

The (one-dimensional) wave equation is the second-order linear partial differential equation $$\frac{\partial^2 f}{\partial x^2}=\frac{1}{v^2}\frac{\partial^2 f}{\partial t^2}\tag{second order PDE}$$ ...
5
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3answers
703 views

What is the mass of a wave?

The slide called "QUANTA" here says that "One Quantum has a definite mass" and the picture shows a wave. So, What is meant by the mass of a wave?
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2answers
188 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 ...
7
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1answer
114 views

Minimal Extension of Wave Equation to Include Dispersion

Let's say you are modeling some process with the wave equation $\frac{1}{c^{2}}\frac{\partial^{2}\psi}{\partial t^{2}} = \nabla^{2}\psi$. You wish to improve your model by including dispersive ...
7
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2answers
329 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 ...
7
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2answers
464 views

How does infrared light 'erase' phosphorescence on zinc sulfide?

I found some sheets of zinc sulfide in my basement that phosphoresce green for up to 24 hours or so after exposure to bright light in the violet range or shorter. One of the first things I tried was ...
6
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2answers
341 views

Will a wave packet undergo dispersion when traveling down a hanging rope?

Suppose I tie one end of a rope to my ceiling and the other end to a spot on my floor directly underneath it. Because the rope has some mass, the tension varies along the rope, from highest at the ...
4
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3answers
4k views

Why can't light pass through walls but sound can?

When I sit in a room I can hear voices coming from the adjacent room but the light in adjacent room does not enter my room i.e. sound waves travels through the wall but light waves can't. Why?
3
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2answers
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What is light, and how can it travel in a vacuum forever in all directions at once without a medium?

I know there are many questions that are similar (maybe identical?). I am not a physicist nor a student - I am just interested in physics and have been watching many physics channels on youtube ...
3
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3answers
381 views

waves on water generated by a falling object

Let an object of mass $m$ and volume $v$ be dropped in water from height $h$, and $a$ be the amplitude of the wave generated. What is the relation between $a$ and $h$. How many waves are generated? ...