Questions tagged [waves]

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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43 views

Electromagnetics - how to choose a proper normal vector?

In D.K.Cheng's equation 8-29 he makes the following correlation between the magnetic field intensity $\mathbf{H}$ and the electric field intensity $\mathbf{E}$ in an electromagnetic wave. Where $\eta$...
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Waves velocity on a cosmic string

I'm trying to understand a few things about cosmic strings in cosmology. Consider a single string of energy density $\rho$ and tension $\tau > 0$. I don't assume $\tau = \rho$, as apparently most ...
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Diffraction pattern for L-shaped slit

Suppose we have an $L$-shaped slit. The hands of $L$ are of equal length. Consider their $breadth<<length$. How will the Fraunhofer diffraction pattern corresponding to this slit look like?
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Why is intensity of an electromagnetic wave independent of its frequency?

In electromagnetic theory, we define electromagnetic waves as two fluctuating electric and magnetic field which travel in a direction. We have a property called Poynting vector which is the power per ...
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What is the physical meaning of frequency in the wave concept?

Treating light as a wave, we define its frequency. We see that light with different frequency have different colour. But, why? In wave, what property or physical meaning does frequency provide?
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How to find the fraction of the power transmitted between the source and the receiver for the dominant modes of the guide?

The problem is as follows : The inside of part of a square aluminum metal guide ($\epsilon_r ' = 1.00 $and $\sigma_c = 3.54 × 107 [S / m]$) was infiltrated with water ($\epsilon_r ' = 80$ and $\...
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Why is the end of a swinging chain diagonal when $J_0(0)$ is flat?

I'm trying to understand the Bessel function $J_0$, and how it describes the motion of a vibrating hanging chain, and I'm confused by the behavior of the free end of the chain. The derivative of $J_0(...
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How to calculate Phase Difference in this question? [closed]

I have stumbled upon this question: Among two interfering monochromatic sources A is ahead of B in phase by 37°. If the observation is taken at point P such that PA - PB = λ/12 (λ is the wavelength of ...
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Why do we sometimes use the entire particles energy and sometimes only the kinetic term to express a particles wavelength?

In the relativisitc case, the de Broglie wavelength formula can be derived in the following way: $$\gamma E_0=\hbar\omega=h\frac{c}{\lambda}\rightarrow\lambda=\frac{hc}{\gamma E_0}$$ In the classical ...
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Which type of waves are matter? [duplicate]

Since all particles also show wave like nature. Do we know that which type of waves they are? I know they are matter waves but is it an electromagnetic or mechanical waves?
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The wave nature of light

Light is an electromagnetic wave composed of electric and magnetic components. I recently read that the velocity of light is in the direction $\mathbf{E}\times\mathbf{B}$ where $\mathbf{E}$ and $\...
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What is $\dfrac{\partial x}{\partial t}$ in a progressive wave?

I actually divided the velocity of a particle in a progressive wave $\dfrac{\partial y}{\partial t}$ to $\dfrac{\partial y}{\partial x}$ and got $\dfrac{\partial x}{\partial t}$. Which is equal to $\...
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Zero energy for two opposite traveling waves

Is it possible for two waves travelling the opposite way on a rope of some finite length $L$ (connected to two infinite ropes on the edges) to have a total of zero energy? For example, if we look at: $...
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Comparison of wave nature of light and sound

Let two people A and B be standing around a corner, such that none of them can see the other. If A shouts, we know that B can hear it and the vice versa is true as well. My doubt is why does this ...
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Making sense of cavity in a 3 ropes system

I fail to understand why cavity resonance happens. Let's say for the sake of example we have 3 ropes, the first and the last half-infinite and the middle one is of some length $L$. Now, we generally ...
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How to calculate the fraction of the incident power that is reflected? [closed]

I could use some help and justification with the following 3 subquestions since I have no background regarding this topic. Any help would be grateful. We are considering a plane wave of light, ...
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Applying Doppler's effect when both source and observer are same

I was solving this question that describes a situation where a train is moving towards a stationary object and the driver hears the reflected sound. My thought My ...
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Electromagnetic plane wave Mathematica representation [closed]

I've been searching for a working way to represent an Electromagnetic plane wave with Mathematica and with the arrowheads like in the following picture, but I haven't been able to achieve my goal. If ...
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Error in an argument for classical transverse Doppler effect

I was recently reviewing the classical Doppler effect for intro physics students. One aspect of such is that there's no transverse effect: An observer moving perpendicular to the motion of a plane ...
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What are matter waves made of and what is their speed?

We know electromagnetic waves are made of oscillating electric and magnetic fields that can travel at the speed of light without a need for a medium. But, how about matter waves proposed by de ...
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Spacetime as a medium for electromagnetic waves? [closed]

We typically break waves into two separate types mechanical waves and electromagnetic waves and treat them entirely differently based primarily on the observation that electromagnetic waves don't ...
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Feedback: How does the string length affect the motion of a coupled pendulum? [closed]

For an upcoming lab, I want to investigate the relationship between the lengths of the pendulums and the motion of the coupled pendulum. What kind of physics would I need to look into, and would any ...
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Waves and guitar frets

I have a problem to solve for Physics III at university and I can't seem to understand how to solve this question. I have the fundamental frequency at $440$ Hz, $L=1$ m, and $ρ=0.002$ kg/m. After ...
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What is the resultant of four sine waves? [closed]

Four sinusoidal waves move in the direction of the positive $x$ axis through the same rope. The frequencies are in the ratio of $1:2:3:4$, and the amplitudes are in the ratio of $1:\frac{1}{2}:\frac{1}...
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Phase of a wave in relativity

Take a one-dimensional plane wave $\exp(i(kx-\omega t))$. How can I show that its phase is a $Lorentz \ Invariant$? How to derive the form of $4-wavevector$?
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Dispersive relation in quantum wave mechanics

Question 2. For nonrelativistic free particle $E=\frac{p^{2}}{2m}$ and using the de Broglie relations the corresponding dispersive relation becomes $$\omega(k)=\frac{\hbar k^{2}}{2m}$$ Then following ...
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Which expression represents a plane wave propagating in free space? [closed]

Using the usual notation for rectangular (Cartesian), cylindrical, and spherical coordinates, which of the following expressions represent a plane wave propagating in free space? $$e^{-jk_0R\sin(\...
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Intensity of light passing through polarising filters

I came across a question in my Textbook which I am unsure about. Two polarising filters are aligned to transmit vertically polarised light. They are held in front of a source of horizontally ...
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Properties of matter waves

Can anyone explain me the meaning of this line? "Velocity of matter wave depends on velocity of particle generating it"
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Why solutions to the wave equation with constant frequency in time have exponential form?

I am reading about the solutions to the wave equation through a separation of variables (time and position): $H(x,t)= A(x)B(t)$. But since the solutions we are seeking are solutions with constant ...
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1answer
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EM Wave Reflection and Transmission Between with Anti-Reflective Coating

I am trying to solve a problem in which light is normally incident on a material of refractive index n which is coated with an anti-reflective coating of refractive index $n^{\frac 1 2}$ and thickness ...
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Vibration of particles in EM waves

We can find the direction of vibration of a particle by shifting the wave in the dirction of wave travels. Is this applicable for EM waves as well?
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What is the intuitution behind a wave with zero wavenumber?

I was recently solving a physics problem that gave you the electric field $$E(x, y, z, t) = E_{0}cos(k_{y}y + \psi_{y})sin(k_{x}x-{\omega}t)\hat{z}$$ and the question asked for a variety of things ...
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Wavefronts, refraction, and the marching soldiers analogy

I am not a physicist, but rather a middle school science teacher. Please be gentle. The marching soldiers has been a really good analogy for explaining why a change of direction is caused by hitting ...
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What exactly is fringes in interference of light?

In Young's double slit experiment interference patterns are formed. And my question is what is meant by "fringe". Is it only dark band or bright band? I am confused because formula for ...
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Speed of speaker vibration

I have a problem of understanding how to find the velocity of a speaker membrane Take air pressure to be $p=105 kPa$ and $T=300K$. A speaker with a circular membrane of diameter 10 mm sends out sound. ...
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Looking for a formula to describe this graph, related to wave mechanics

I'm working on a statistics problem looking to understand why some very simple periodic models are causing even cutting-edge Bayesian sampling tools to fail catastrophically. I think I've traced the ...
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Finding the Full width half maximum of a function

I am a bit confused as to how we calculate Full-Width-Half-maxiumums (FWHM) of a function. Consider a function as $$f(x) = {\frac{\sin(ax/2)^2}{(ax/2)^2}} \cos(bx/2)^2 $$ where b>>a. It looks ...
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Why is String Stiffness Proportional to the Fourth Spatial Derivative of String Displacement?

I recently watched a lecture on dispersive medium. I understand that if you disregard the idea that a string is ideal, you must add a stiffness factor into the wave equation. From that you can derive ...
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In ultrasound, why doesn't the reflected sound gets reflected again on its way back?

Consider the diagram below illustrating how A-scans work, why doesn't some of the reflected sound on its way back at the red circle interface reflect again (thereby reducing the signal intensity ...
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Angle of refraction of water in relation to temperature [closed]

I am an IB diploma student working with the angle of refraction of water. My goal is to note the change in the angle of refraction with temperature. However, I havent found any noticable change in my ...
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Do we take into account the physical angle between Electric fields and Magnetic fields during interference of light?

I have been studying interference of light waves for a while now and I have a doubt. I have never seen any sources (books, internet , teachers) ever take into consideration about the "actual"...
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Why does “$|E|^2 \propto $ the number of photons” follow from “$\epsilon_{photon} = hf$”?

For my introduction to quantum physics course we are using the book "University Physics volume 3", availabe here, in the linked chapter in the first paragraph of the "Using the wave ...
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Wave nature of a typical ball [closed]

how we can observe the wave nature of a typical tennis ball. Construct a thought experiment
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Why is this electromagnetic field a wave?

In D.K.Cheng's Field and wave electromagnetics he states the following: The phasor electric field intensity for a uniform plane wave propagating in the +$z$-direction is $$\mathbf{E}(z)=E_0e^{-jkz} $$...
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BCs at 2D anisotropic media

I have 2D an-isotropic meta-surface with surface admittance $G = \begin{bmatrix} G_{xx}& G_{xy}&0\\ G_{yx}&G_{yy}& 0\\0&0&0& \end{bmatrix}$; the rest of the space is just ...
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What is the physical meaning when we say complex waveform has an energy at certain frequency?

We say that a complex periodic wave has an energy at certain frequencies. Or we can also say that such waveform has a certain “frequency component”. I understand that mathematically it means we can ...
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Does electrical sawtooth wave actually produce sinusoidal oscillations at harmonic frequencies?

According to Fourier's theorem, we know that a sawtooth wave can be represented as a sum of sine waves. These sine waves we know as harmonics (in the context of sound). My understanding is that it is ...
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Tension on a rope

I was wondering how can one describe the tension force in a continuous way along a rope. We can look at a rope segment of length $dx$ and say the net tension force is $$T\sin\theta_{x+dx} - T\sin\...
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Can a particle transcribing motion described as $y=(\sin x)^2$ be called to be in vibration? [closed]

I know that $\sin x$ or $\cos x$ curves can be said to be "in vibration," but what about $(\sin x)^2$?

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