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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Standing waves on compound string

Please help with this question - No data is given as such. The 2 strings have different thickness. Initially, minimum frequency of the thick string is 120 Hz. Then if we push the cart such that only ...
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143 views

Why do we hear better during the night? [duplicate]

At night, we hear weak and far sounds approximately clear, while during the day we cannot. My high school physics teacher was saying that “this is because of interference of sound waves. During the ...
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135 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 sin(...
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Trying to read phase shift constant from the graphs

I have an equation $y(x,y) = y_0 \sin (\omega t \pm kx \pm \phi)$ and there are two graphs. One is $y(x,t=0)$ in units $mm(mm)$ and the other is $y(t,x=0)$ in units $mm(s)$. Now I have to find all of ...
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1answer
30 views

Group Velocity of guassian packet equals time derivative of mean position?

If I look at a gaussian wave package, and then interpret (in the usual Quantum-Mechanics Way) its square value as the propability density, then I can calculate a mean value for the position: $$ x_{...
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1answer
189 views

Energy and the modes of standing waves

If you induce a higher mode in a standing wave, does the wave then carry more energy? If so, does that differ for a mechanical or EM wave? (Perhaps I should elaborate on why I am asking this question:...
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2answers
127 views

Why do some types of waves disperse?

We know that some mediums/waves are non-dispersive such as air for sound waves, and waves on a string. But, why do some waves, for example deep water waves, disperse? I am trying to understand the ...
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1answer
23 views

Curious about headphones [on hold]

So I'm trying to learn more about headphones. I have a small piston that is in a small sealed volume (the earcup, say it is $25\, cc$). And there is a front volume between the piston and the ear (...
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1answer
123 views

Is meters per second equivalent to seconds per meter?

I know this question is probably ridiculous, but bear with me for a moment. This thought emerged while I was converting between nm and wave numbers ($\rm cm^{-1}$). In order to prove this conversion, ...
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1answer
123 views

Is dispersion a property of medium or wave

I got a problem in learning Lewin's 'Vibration and Waves'. He first solve the eigenvalue of 5 beats connecting together and with fixed boundary condition. Then the velocity for different modes are ...
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1answer
26 views

Standing waves due to two counter-propagating travelling waves of different amplitude

Suppose I have two counter-propagating travelling waves of the same frequency but of different amplitude, like the transverse waves produced in a string by partial reflection off an endpoint. I read ...
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34 views

Relative velocity between phase velocity wave and a group velocity wave

It is said that material particles have a dual nature. A particle is associated with a wave which travels with phase velocity and the particle travels with group velocity. These are related by $$v_\...
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Beats: frequency of resulting wave vs. beat frequency

The beats frequency heard from the interference of two sound waves with frequencies $f_1$ and $f_2$ is $$\nu=|f_1-f_2|$$ Nevertheless the frequency of the resulting wave is not $\nu$ but the mean ...
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3answers
108 views

Significance of wave number?

Till now all I know about the wave number is its formula i.e. ${\frac{2\pi}{\lambda}}$. I always wanted to know what it really means. So can anyone please, explain me its physical significance?
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25 views

Sound waves - physics [on hold]

A closed organ pipe of length L is in resonance with tuning fork. If a hole is made at a distance L/4 from the closed end will there be resonance again? If so when?
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184 views

Treating matter waves as light waves?

Is it valid to treat a matter wave as a light wave with wavelength equal to the de Broglie wavelength of the matter wave? Either way please can you explain why?
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3answers
53 views

Can sound travel in the form of transverse waves?

We all know that sound is a longitudinal wave but in some books, I have found that sound travels in the form of both longitudinal and transverse waves while passing through rocks. Can anybody explain ...
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25 views

Waves: Phase Difference [on hold]

I know this is a somewhat elementary question, but I have always had some trouble mastering this material (this kind of question in general): Suppose two microphones are the same distance from a ...
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0answers
24 views

Conditions to find standing waves harmonics

I came up with a doubt on standing waves conditions. The type of question I find difficult to answer is of the following type. Consider a rope. I do not know if the rope is fixed at both end or at ...
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1answer
230 views

Why does amplitude of a mechanical wave increase and then decrease with increasing driving frequency?

I was doing an experiment where I explore how the frequency of the oscillation of a vibrating water hose (the end of the water hose), affects the amplitude created by the water path (a wave-like ...
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1answer
32 views

Situations in which there is path difference interference or formation of standing waves [on hold]

I came up with a doubt about standing waves and path difference in general. Consider these two different cases as examples. If I have a rope fixed at one end and I make the free end oscillating, I ...
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3answers
506 views

Is there any effect on mechanical waves by electromagnetic waves (and vise versa)?

Do electromagnetic waves like light and gravitational waves (due to moon for instance) affect on mechanical waves like sound? Can sound change the path of light?
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1answer
37 views

Vibrations of a string [closed]

A string with length $L$ is stretched between two fixed points. The string can't vibrate with which wavelength? Four options are given, namely $L$, $L/2$ , $2L$ and $4L$. I know that the ...
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25 views

Wave equation for odd spacetimes and source terms

It seems to be quite common practice, when solving the wave equation in spacetimes with odd topologies or horizons, to decompose the solution into a sum of the various origins (or destinations) of the ...
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1answer
2k views

Why do you only hear the bass when someone nearby is wearing earphones?

When someone nearby is listening to music through earphones or headphones, usually you can only hear the bass (unless it's really loud where you can hear the singer's voice and the other instruments ...
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40 views

Mechanical energy in an harmonic wave and in normal modes

I think I miss something about energy of a mechanical wave. In absence of dissipation the mechanical energy transported by an harmonic wave is constant. $$E=\frac{1}{2} A^2 \omega^2 m$$ But, while ...
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2answers
120 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 ...
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1answer
58 views

Conservation of energy in interference of light

In interference of light, I know that energy is conserved globally but how the energy disappeared at minima appears at maxima? Is there any path by which energy flowed or is it just energy couldn't ...
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0answers
33 views

Did de Broglie deduce E=pc? [closed]

IIUC, $E=mc^2$ follows from $E=pc$ if $p=mc$ and $pc=hf$ is the same equation as the deBroglie wavelenth. Is it safe to say that $E=pc$ is an equation by de Broglie or is that equation some other ...
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1answer
16 views

What happens when sound source is radiating through a hole in a cavity?

What happens to the external sound field , when loudspeaker attached to one wall is radiating inside a box and other wall has a aperture size of a diaphragm? Do we experience Helmholtz effect?
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3answers
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Water in glass tubes producing different pitches when tapped. Why exactly is this?

So I've been making a DIY instrument for my physics project at school. I decided to try this experiment where I put different volumes of water into a glass cup, and I tap it with a spoon to create ...
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2answers
404 views

Wave packet in curved spacetime

It is known that the classical equation of motion for a scalar field wave packet on a curved spacetime background gives the geodesic trajectory (the e.o.m. is $(\nabla_\mu \nabla^\mu + m^2) \Phi=0$). ...
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2answers
50 views

What is the difference between real value and abs value? [closed]

I am confused here, though I have been reading about it for years. What is the difference between a real value and an absolute value? For example, when do we take the absolute value of pressure or the ...
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2answers
127 views

Minimum frequency of an electromagnetic wave

Is it possible to create an electromagnetic wave of near zero frequency? An electromagnetic wave carries energy. If we can make the frequency of an EM wave vanishingly small and make it practicality ...
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3k views

Low frequency electromagnetic waves

Some frequencies of electromagnetic waves are used for transmission of information, like radiowaves, microwaves, light, but some are not.. What about low frequencies? Perhaps low frequencies aren't ...
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2answers
200 views

why does the frequency of a wave remain constant?

They say the frequency of a wave is its fundamental character, thus remain constant throughout its propagation regardless the medium through which it travels. Could anyone explain why frequency of ...
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2answers
46 views

Why monochromatic waves exist even theoretically

I was reading this question. Where the author made a statement that If I take a wave with period T, it is also true that it has a period 2T, 3T and so on. That is, it has frequencies of 2π/T, but ...
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Why are FM radio waves less susuceptible to interference than AM? [duplicate]

When studying modulation of radio waves (or of most electromagnetic waves for that matter) I came across that question. Why are FM waves less susceptible to interference than AM waves? I know that in ...
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2answers
214 views

Period of double slit experiment

What is the period of the pattern from the double slit experiment? It varies along the pattern right? Namely I'm confused because when considering two point sources (See: Period of Interference ...
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37 views

Is there any solution manual to A.P. French's 'Vibrations and Waves'?

I'm trying to work through A.P. French's Vibrations and Waves. Unfortunately, I can't check the details of my solutions since the solutions aren't given with the textbook. Does someone know where I ...
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3answers
4k views

How to “derive” the wave equation without refering to strings?

The wave equation in $3$ dimensions is simply: $$\nabla^2\psi = \dfrac{1}{v^2} \dfrac{\partial^2}{\partial t^2}\psi,$$ and the intuition behind this is that at each point of space with coordinates $(...
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light interference [on hold]

Recently while driving, i noticed that when it is dark, the light emitted from an incoming car with its headlights at full strength (bright) and with mine also at the same state, my windscreen sort of ...
4
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1answer
211 views

Diffraction and $k$-space

Regarding diffraction I am a little bit lost reading about reciprocal space and the space of $k$'s. As I understand it the Fourier relationship between a wavepacket $\Psi(\vec r,t)$ and the complex ...
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1answer
22 views

Reason for absorbance

First quoting the example which raised my curiosity"when light passes through polaroid it absorbs certain direction light rays" My question is how this phenomenon of absorbance occurs is this some ...
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1answer
421 views

How does a longer wavelength penetrate deeper with Rayleigh waves?

I'm struggling slightly to understand this idea. I've slowly been building up an explanation, so at this stage it might be just some confirmation I'm looking for, but also some guidance if I'm off ...
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1answer
46 views

Fresnel zone with different antenna heights

I've looked at the formula to calculate the first Fresnel Zone: $$r=17.31 * \sqrt{\frac{d_1*d_2}{f*d}}$$ whereby $d_1$ and $d_2$ are distances from the obstacle to the link end points in meters, $r$ ...
2
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2answers
121 views

Is sonic boom louder than the sounds that a object traveling at the speed of sound makes, if so why?

Here are the wave-front models for both: I am in an introductory physics course. Just learned about this. I am not entirely sure if sonic boom is louder. But from what I saw, it's loudness is ...
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117 views

Intensity of a standing sound wave at displacement nodes?

We know $$P = F\cdot v$$ where $v$ is the velocity vector. Since at the "displacement nodes" in a standing sound wave the velocity of the particles is always 0, the Power must be 0 and hence the ...
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Can localized fluid perturbations be accelerated by pressure gradients?

I would like to know if there are any examples in fluid dynamics (or continuum dynamics) of small perturbations (or waves, solitons, or other "localized" solutions of the fluid) being accelerated in ...
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2answers
58 views

Why do we hear a different timbre when someone speaks with helium (or other gases) in their lungs?

Let me make one thing clear: I am fully aware that the change in timbre comes from the change in acoustic wave speed when going through a different medium (just like light). However, would I not ...