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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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 ...
7
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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 ...
7
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2answers
231 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 ...
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3answers
712 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?
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3answers
888 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 ...
2
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3answers
484 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 ...
7
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5answers
835 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 ...
2
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2answers
789 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.
...
8
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2answers
900 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 ...
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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 ...
4
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4answers
545 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 ...
3
votes
2answers
587 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 ...
5
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5answers
774 views
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 ...
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4answers
417 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?
...
8
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4answers
1k 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?
3
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2answers
588 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?
3
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2answers
636 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 ...
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2answers
584 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, ...
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1answer
165 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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3answers
696 views
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 ...
8
votes
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 ...
5
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3answers
371 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?
3
votes
2answers
1k 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 ...
5
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2answers
269 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 ...
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2answers
178 views
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 ...
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2answers
422 views
Questions regarding standing waves
I have two questions regarding mechanical waves.
1) We know that standing waves are created when any wave traveling along the medium will reflect back when they reach the end. But in an open organ ...
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0answers
42 views
EM-wave hits a brick-wall, $\pi/2$ -phase-shift? [duplicate]
Possible Duplicate:
Phase shift of 180 degrees on reflection from optically denser medium
If I have a cord-wave, I get a phase-shift with attached cord but do I get such a phase-shift with ...
6
votes
2answers
90 views
Relaxation time for deviations from spherical shape of a black hole's event horizon (and waves)
A different question about truly spherical objects in nature (Do spheres exist in nature?) made me think of a lecture I had been at where, as I recall, it was mentioned that the most perfectly ...
5
votes
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 ...
5
votes
2answers
337 views
What are the normal modes of a vertical rope?
Closely related to this question on traveling waves on a hanging rope, I would also like to know what the normal modes are on a rope that hangs vertically, fixed at both ends.
Tension in the rope ...
4
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3answers
184 views
Are two waves being in phase is the same as saying that the two waves are coherent?
If two waves are coherent, is it the same as them being in phase? Please correct if I'm wrong.
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
votes
2answers
945 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
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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 ...
2
votes
10answers
577 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 ...
2
votes
3answers
852 views
How is electromagnetic wave variation distributed in space?
Imagine an electromagnetic wave (a monochromatic one for example)
The electric field amplitude, and its variations travel in the propagation direction.
So, if there really exists a propagation ...
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4answers
155 views
wave-particle duality
I have been trying to understand "wave-particle duality" and other cases related to it. I am currently a college level student. I have few question which I am not getting answers clearly.
In double ...
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2answers
875 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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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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2answers
348 views
Through a lens, which light beam reaches the screen first?
Imagine three light beams are "sent" to a lens simultaneously, they start at the same position but move towards the lens at different angles. The first light beam passes the lens at its edge, the ...
0
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1answer
154 views
Transmission of Gaussian Beam Through Graded-Index Slab
The $ABCD$ matrix of a glass graded-index slab with refractive index $n(y)=n_0(1-\frac{1}{2}\alpha^{2}y^{2})$ and length $d$ is $A=\cos(\alpha d)$, $B=\frac{1}{\alpha}\sin(\alpha d)$, $C=-\alpha ...
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3answers
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Why electrons behave as a particle and also as a wave?
Why do electrons (and other very small particles) sometimes behave as particles (i.e. when we are not looking at them) where as other times they behave as waves?
