# Tag Info

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I believe this question is not worded correctly only because the submitter is not that well versed in scientific terminology. To put it briefly - neither sound waves nor light waves have mass, that is because they are representations of moving particles, they themselves are not entities and do not exist beyond the scope of human-facilitating terminology. As ...

6

Lets suppose the amplitude of each wave is $A$ and thus intensity will be $I_0 =A^2$. After superposition amplitude of the resultant wave becomes $2A$. but intensity becomes $I=(2A)^2$ Implies $I=4A^2 =4I_0$

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The only thing that separates visible light from x-rays and gamma rays is wavelength. Here is a brief explanation of light, and a chart that compares wavelengths of different portions of the electromagnetic spectrum, including visible light: http://www.andor.com/learning-academy/what-is-light-an-overview-of-the-properties-of-light As you can see, the ...

4

Actually, the light beam does not follow the shortest path, but rather the faster path. Else the light would not bend but go straight there. This is Fermat’s principle. what point is the photon trying to reach? Good question. This point you are talking about, is in fact your eye. A straw in a glass of water visually bends at the interface. Look at ...

2

For the modeling of surface wave motion there are only two restoring forces to consider: surface tension and gravity. Compared to gravity, surface tension forces are very weak and therefore have a greater influence on the regime of the smaller, capillary waves. Waves in deep water carry away the energy dissipated by shear wind forces - perhaps from a storm ...

1

For any arbitrary collection of such travelling waves will always be a wave envelope that retains the same shape as the collection of waves propagate? No, it will not. For example, a Gaussian wave-packet will spread out in time. Wave packets are used to represent localization of particles in Quantum Mechanics.Group velocity will give the physical velocity of ...

0

If you are measuring the radio waves at a single point all you can measure is the direction and the field strength. To find out how far away the source is you need a second measuring point at some distance from the first one. If you measure the direction from two different receivers you can use the difference in the direction to locate the source by ...

4

It is commonly believed that the speed of sound at high densities is bounded from above by $c/\sqrt{3}$, where $c$ is the speed of light. Calculations of this quantity in many theories, ranging from QCD to systems with scale invariance, have all shown it to either stay below or exactly saturate the bound. See the introduction of this paper for a recent ...

2

You have that $$E=2A_0\cos\left(\frac{\phi}{2}\right)\sin\left(\omega t + \frac{\phi}{2}\right)$$ which is correct. To get the intensity, you then square and time average this: \begin{align} I=\langle E^2\rangle&=4A_0^2\cos^2\left(\frac{\phi}{2}\right)\left\langle\sin^2\left(\omega t + \frac{\phi}{2}\right)\right\rangle\\ ...

2

This diagram would help. You need to approximate the two longer sides of the trangle to be parallel to obtain $\varDelta l = d \sin \theta$. Source: http://www.wikipremed.com/01physicscards.php?card=876

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Hamilton's principal of least action would apply which is more general than Fermat's principle. If Energy remained constant then action would be proportional to time so probably something like Fermat' principle would apply, but this is just a guess.

1

First of all ,what is unpolarized light? As Feynman said, ''Light is unpolarized if you cannot tell whether it is polarized or not.'' light from ordinary sources are unpolarized because our detectors only can detect the mixture of waves polarized in different directions.(not individual waves). waves emitted by any one molecule may be linearly polarized ...

1

Maxwell's equations of electromagnetism don't allow an electromagnetic wave to just sit there without moving in empty space (in the absence of electric charges). An electric field is created by a magnetic field changing in time, and vice versa, so the coupled fields have to be changing in time (i.e. propagating) in order to exist and sustain themselves.

2

Using a process called interference, we can find wavelength, because the way that waves interfere is reliant of wavelength. Interference is based off of two key principles of waves: they are made up of peaks and troughs. When troughs overlap, they go lower. When peaks overlap, thy go higher. When a peak meets a trough, they cancel. Of course, the positions ...

1

The wave came back to him after 3.5s passed. That gives a clue as to what kind of signal this was (and wasn't). It wasn't electromagnetic radiation (e.g. light). It was sound. Sound is a wave carried by a medium, in this case, air. The velocity of the source of a sound has no effect on the velocity of the propagating sound wave. This gives you the ...

2

In this case the wave is a sound wave i.e. a compression wave moving through air. The velocity of the wave is determined by the elastic properties of the air. Specifically it is given by: $$v = \sqrt{\gamma\frac{P}{\rho}}$$ where $P$ is the air pressure, $\rho$ is the air density and $\gamma$ is a constant called the adiabatic index. So for any given ...

1

You can show this by noting that $k_1^2=k_2^2$ and $X(x)T(t)= F(k_1x\pm k_2vt)$. You can see that by: $${ \partial^2 f \over \partial t^2 } = v^2 { \partial^2 f \over \partial x^2 }$$ Is more common take $k_1=k$ and $k_2v=-\omega$. Then you may note that the equation imposes the choices of $k_1$ and $k_2$, or $k$ and $\omega$. The imposes is ...

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Hint: Use light cone coordinates. What is the full solution to $$\frac{\partial^2 f(x^{+},x^{-})}{\partial x^{+}\partial x^{-}}~=~0~?$$

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Consider showing that $f_L$ and $f_R$ are themselves solutions no matter what function (of one variable) they are. Next consider any particular solution (i.e. with particular boundary conditions). Then try relating your boundary conditions to a particular $f_L$ and $f_R$ jointly. If you have a result about uniqueness, then you know exactly how many ...

1

A solution to the Schrodinger equation for a free particle is a plane wave, and because any combination of solutions is also a solution we can construct solutions by summing up plane waves. The equation you quote is constructing a solution by Fourier synthesis. Since the plane wave function $e^{i(kx-\omega t)}$ is a solution we can use Fourier synthesis to ...

1

Look at the original, Heinrich Hertz, 1889! If E=B=0 on a plane, S=0 => no energy Transport through that plane. I agree with Annix: "The pictures may be depicting a static wave, but certainly, not a propagating wave."

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Astute observation, and very interesting phenomena. I do know for a fact that the reason the column of water narrows as it gets further from the faucet is due to acceleration by gravity and an increasing fluid velocity. The higher the velocity, the lower the pressure. Since the pressure outside everywhere along the column is essentially the same, the column ...

1

When you first start moving the end of the rope, there will be points along the rope that are not yet moving, and have not experienced the greater tension that results from your motion. It stands to reason that as these points first "feel" the wave, they will move towards the source of the wave (where the tension is greater) as well as transversely. If that ...

0

John is right. I just want to try to give a more intuitive explanation. Suppose you plot the sine and cosine of a wave that has a wavelength of exactly 1. Then of course the peaks and zero-crossings would be exactly 1 unit apart. Now suppose you put an envelope on that plot, such as multiplying it by $x$. Here's that plot: Notice the zero-crossings of ...

0

In an alternating current circuit the electric current changes his direction periodically, by definition. Thus, if you look at the voltage magnitude, i.e. the magnitude of the electric potential $$\mathbf E = \nabla V$$ where $\mathbf E$ is the electric field; it will have a periodic shape. The changing sign of the magnitude states the inversion of the ...

0

Nobody explicitly uses the proper units for amplitudes, the square root of (action divided by the product of all your axes/variables). Instead, one usually expresses this fundamental quantity using two conjugate variables. For example, if you regard a simple mechanical oscillator as a wave by looking at its status over time, the interesting quantity (action ...

1

It's not volts per millisecond, it's volts at particular milliseconds. Think of the wave as displayed on an oscilloscope. Waves can actually be anything as a function of anything. It's just that voltage as a function of time is a really nice example. Of course, when you're talking about Fourier transforms, you get into complex numbers. For example, you can ...

0

Why do you say there is a phase shift at transmission into the first medium? You get a 180 degree shift at both the reflection on the front surface (air - coating) and on the second surface (coating - glass). You want these two reflections to be out of phase, so the round trip in the coating needs to be 180° also. That means total thickness of $\lambda / 4$ ...

1

You could consider omega to be a pure indicator of periodicity in the cycle. Larger omega gives you more rads per second. Larger omega gives you shorter wavelength, and therefore more energy required to keep the cycle going. You can look at omega in the equation and get an idea of the amount of energy you are dealing with.

1

One of the most useful ways of describing SHM is obtained by associating it with the projection of uniform circular motion. Imagine that a disk of radius $\mathit{A}$ rotates about a vertical axis at the rate of $\omega~\text{rad/s}$. Also imagine that a peg $\mathtt{P}$ has been attached to the edge of the disk and that a horizontal beam of parallel light ...

0

An electromagnetic wave is a transverse wave, and we can make an electron and a positron out of it in pair production. Then we can diffract the electron, and even refract it. We can also polarize electron beams. Then we can annihilate the electron with the positron, and get two or three electromagnetic waves, which are transverse waves. So the hard ...

2

The point of restricting the string to length $L$ is that we can then construct a periodic function (with wavelength $L$) by imagining repeated copies of the string connected to each other. In this case we can construct the function as a Fourier series with the lowest frequency sine/cosine having the same wavelength $L$. If we have an infinite string then ...

4

we all know waves are of two types transverse and longitudinal, and we do have studied about de broglie wave as well,so which ond of them is it?. or we have other means to classify them.. For a wave to be either transverse of longitudinal it must be a vector field quantity (e.g., the electric field). This is because "transverse" means that the ...

3

To the point of Is it hard to measure the resonant frequencies directly: it's tricky and careful discussion of the measuring procedures is needed. Some of the main problems: Destruction of the open-end behavior: If you place the speaker and microphone in front of the vocal tract to measure the response, you may have just switched open end behavior of your ...

5

It is tempting to think that if something is moving there must be a force that keeps it moving. However ever since Newton formulated his first law of motion we know this isn't the case. An object, whether it's a massive object or a light ray, will carry on moving at a constant velocity unless some force acts on it. So nothing is needed to keep the light ray ...

4

There are two primary factors that allow the cochlea to isolate frequencies. These are generally referred to as passive and active properties: tl;dr version: The passive properties are due to the mechnical properties of one of the membranes in the cochlea, the basilar membrane, primarily the width and stiffness at a given point. The active properties are ...

2

According to maxwell's electromagnetism, a changing magnetic field gives rise to electric field, and a changing electric field gives rise to magnetic field lines.. So simply put, when a changing field of either type(electric or magnetic) is produced it gives rise to its counter parts (magnetic and electric).. So once a changing field comes to existance ...

2

The slinky approximation is essentially the assumption that the extensions we are dealing with (including the equilibrium length) are much greater than the natural length of the spring. For example, this is true in a slinky, which stretches to much greater lengths when you pull it than its natural length. Thus, while we would normally have, for a length $x$ ...

1

The theories of tidal pull, planet's rotation etc are good and promising, and almost explain the phenomenon that causes the great tsunami waves on Miller's planet. But here is another theory: Because of the time slippage. A planet that near to a black hole, if there is time slippage occurring (7 years per hour), this cannot be uniform all over the planet. ...

2

I think The Physics of Musical Instruments (Springer Science & Business Media, 1998) by Fletcher and Rossing would be a good starting point for you. The general physical description of sound rests on the investigation of the impedance changes on the boundaries. For example: the reflection at the end of the string is caused by the discontinuity between ...

3

The resonances are quite broad: each cavity will amplify a broad range of frequencies, spanning most of or more than an octave. Driving those resonances isn't as simple as choosing a pitch. You have to do some work to efficiently couple the different cavities to your vocal apparatus, and to maintain the resonance while you're singing. The people who are ...

0

Without going into wave equations, lets just say the segments of a string does not only move along the vertical direction. There are horizontal movements as well, although to a much smaller amplitude. A segment is being pulled towards the source horizontally when departing the equilibrium position and pulled back when heading back from maximum amplitude. ...

-3

According to quantum mechanics, $p=\frac{h}{2\pi}k$,where $k$ is wave vector and $h$ is Planck's constant. As we know $k={2\pi\over \lambda}$, where $\lambda$ is the wavelength of the wave. So momentum and wavelength are associated to each other. Moreover we can view as the motion of the every particles as well as wave and particle.This is known as duality ...

1

It should be seen more like: A stationary charge generates an electromagnetic field A moving charge generates an electromagnetic field An accelerating charge generates an electromagnetic field So the hierarchy/pattern you mentioned isn't really much of a hierarchy/pattern after all. But actually, you can show that only the second derivative enters the ...

0

Is there an object I can put on my body that would allow me to feel the bass of the music more, without picking up the vibrations from the ground? Anything rigid and lightweight will convert the sound pressure more effectively into force. That's why loudspeakers have cones. I know sound waves are redirected if they hit an object, but is there ...

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Cicle is the smallest repatable segment between two points, where: 1. These point lies on one line and the line is parallel to direction of wave propagation. 2. These two points have the always same sign of slope. Thanks to Floris in help of derivation of the definition.

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$\omega_{3}$ and $k_{3}$ are the frequency and wavevector of the generated wave. As you mentioned above, we are sort of looking at: $\omega_{3} ~=~ 0~,~ \pm (\omega_{2}-\omega_{1})~,~ \pm 2 \omega_{1}~,~ \pm 2 \omega_{2}~,~ \pm (\omega_{1} + \omega_{2})$. The names for these, respectively, are: optical rectification, difference frequency generation, ...

0

It sometimes occurs. It is called sonochromism. Here is my source.

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Without the phase change energy conservation would not be satisfied. To see why this is true you can think of a simple Michelson interferometer; without one of the fields having a phase flip you could get constructive (or destructive) interference at both sides of the beam splitter which would result in twice (or none of) the energy which you sent into the ...

0

It helps to realize that for the string, "hard boundary" means the displacement dy/dt=0, whereas for a soft boundary it means the force F=0. In the non-extreme cases, neither dy/dt nor F is zero. Their ratio will determine the phase. It's fairly clear that you can't have both F = 0 and dy/dt = 0 at one end, and there aren't any other relevant variables ...

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