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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Does the standing wave equation proof require $\ell=Nλ$?

Consider two identical sources $S_1$ and $S_2$ of waves, separated by a distance $\ell$ (as shown in the figure). The sources produce waves in opposite directions(and towards each other). Now, ...
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Why is it always $\psi= A \sin kx + B \cos kx$ to solve a wave function?

Why is it always $\psi= A \sin kx + B \cos kx$ to solve a wave function instead of the one with $e^{ikx}$? Both are the solutions but the one with $e^{ikx}$ is seldom used.
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Why does an antinode form at the open end of an organ pipe?

I recently learnt about reflection of waves in various media and the resultant standing waves formed. In a string which is tied at an end, the wave formed reflects with a phase difference of 180 (at ...
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1 answer
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How do retinal cones see color when the cones pickup photons and not waves?

I am wondering how cones (photoreceptors in the retina) can see color if colors are wavelengths but cones send signals when they absorb photons. Maybe by using the energy level (or only being ...
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Phase Difference of A Mass-Spring System For Different Starting Points [closed]

I’ve seen a very similar question (almost identical) in a test, but the answer key of the test said that it's quarter of a cycle (90 degrees). I'm a bit confused. Are they the same if you subtract 90 ...
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Is there a limit for passing of classical waves behind a slit?

For the classical waves is there a limit for them to pass through a slit when the dimentions of the slit are much smaller then the wavelength? I think that the Hyugence principle must be valid and ...
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Can we tell anything about the velocity at which a spherical stone falls into a lake based on the sound it makes?

Suppose we have a spherical cow... I mean stone, and we throw it to a lake. Can we tell anything about the velocity (speed and angle) at which it falls based on the sound it makes? And based on a ...
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What, precisely, using mathematics, is meant by "electric field with only an $\hat{x}$ component"?

I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following: The Helmholtz Equation In ...
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1 vote
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Pressure wave speed $v=\sqrt{\frac{B}{\rho}}$ rearranged $\rho v^2=B$ is similar to kinetic energy: $E_k=\frac{1}{2}mv^2$. Is this a coincidence?

The speed of a Pressure wave speed is given by: $v = \sqrt{ \frac{B}{\rho}}$, which seems rearranged very similar to kinetic energy: $\rho v^2 = B$. How can this be understood, is this a coincidence? ...
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What is the wavelength of light in a practical sense?

Okay, so I know that a wavelength is a distance of crest and a trough added together which makes a whole wave, but what is it in the real sense? Like in the case of sound I know when we say "...
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Can you explain me the definition of wave number as defined in theoretical physics?

Wavenumber, as used in spectroscopy and most chemistry fields, is defined as the number of wavelengths per unit distance. The corresponding formula is $$k=\frac{1}{\lambda}.$$ However, in theoretical ...
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Number of Cycles per Second Emitted by an EM wave [closed]

I was doing a test and I found this question I don't understand. Test Question (Question 34) I went to this link to try and figure it out: https://sciencing.com/convert-photons-joules-8508488.html, ...
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Maximum tensile strain at a point on a standing wave

Objective To find the maximum tensile stress on a wire (of length $l$) at a point $x$ which has a standing wave on it having equation $y=f(x,t); 0 \le x \le l$. My work When the wire is at rest, the ...
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Do long waves propagate through small openings? [closed]

I have done the following experiment: put some water in glass and covered it with glass cover, then put it in microwave for 10 sec. The water was warmed up (The glass doesnt warm when put in oven ...
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How to find the magnitude of the maximum transverse acceleration of a given point on a string? [closed]

A thin string 2.50 m in length is stretched with a tension of 90.0 N between two supports. When the string vibrates in its first overtone, a point at an antinode of the standing wave on the string has ...
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Which procedure could help decide whether a string's total length has a separate effect from the tension?

My AP physics 1 exam is tomorrow. This question is from a practice exam I have but I never really understood the answer Using the setup above, a student tests how the tension in a string affects the ...
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2 votes
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Questions on the Zakharov-Shabat inverse scattering paper

I am trying to work through the Zakharov and Shabat paper on inverse scattering for the nonlinear Schrodinger equation (PDF). I am stuck on section 2. Problem 1. I need to know how to reconstruct $\...
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2 votes
2 answers
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Why is light not a longitudinal wave?

Here is a typical representation of light waves using wavefronts. In the diagram it depicts the peak as the lines and the throughs as the space half way between consecutive lines. Considering light as ...
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Natural frequency of electrons and the Hydrogen atom

Natural frequency is the frequency of a system when it vibrates freely without damping. I am in need of clarification about the definition of natural frequency at the atomic and molecular levels. Let'...
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How do I find the form of a wave equation given initial conditions?

This is probably trivial, but I'm having trouble finding the correct solution given the data I have, and the general solutions to the classical wave equation I know. In essence, I'm being asked to ...
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How to calculate the phase velocity of a partial standing wave [closed]

Partial Standing Waves Partially Reflected Wave A traveling wave encountering an impedance change will be partially reflected and transmitted. It can be represented as the sum of the incident (...
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2 answers
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How many oscillating fields exist in a light wave?

Is light made from one magnetic and one electric field which are oscillating perpendicular to each other? In textbooks, it says that the light can be seen to oscillate in every plane perpendicular to ...
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Can point masses following geodesics and orbiting one another emit gravitational radiation?

I am a bit confused about this situation: according to general relativity, when two masses orbit one another, they emit graviational waves, which carry away certain energy. For example, check out ...
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What is volume of sound?

Is there another term for (volume of sound)? What is the relation between intensity and sound volume?
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Huygens principle and small aperture

Does Huygens principle depend on the ratio of the wavelength and the dimension of the aperture? Do waves extinguish themselves by ratio 10 or more due to interference, e.g. will the wave pass through ...
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How to derive Sommerfeld radiation conditions from Limiting Absorption Principle?

For the Helmholtz equation $$ -(\Delta + k ^2) u = f, \tag{1} $$ imposing the Sommerfeld radiation condition $$ \lim_{r\to\infty} r ^{\frac{m-1}2} \left( u_r - i k u\right) = 0 $$ on $u$ allows us to ...
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How differential wave equation is in general? [closed]

How the differential wave equation is in general? While deriving the equation it is assumed that wave maintains constant shape and constant velocity. Then how can it be a general wave equation as the ...
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Uncertainty of waves

Here in the pictures I have written about some question I have been thinking about a long time, what do you think? Link to the chapter I am talking about: http://www.its.caltech.edu/~matilde/...
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Two Dimensional Hodge Decomposition

In deriving the equation governing propagation of wave in a wave guide, a specific form of Hodge decomposition theorem is used. The Hodge decomposition theorem applied in two dimensions allows us to ...
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Electromagnetic wave in vacuum - Do we have always ${\bf E}\cdot {\bf B} = 0$ and $E = cB$?

In vacuum, but not necessarily into free space, e.g. inside a waveguide, does a EM wave always fulfill the relations $${\bf E}\cdot {\bf B} = 0, \quad E = cB,$$ with $\bf E$ and $\bf B$ the electric ...
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Deriving Solution for Wave Equation Using Retarded Green Function

In the book Advanced Classical Electromagnetism by Robert Wald, it was shown if $\psi$ satisfy the homogeneous wave equation $$\square\psi=0$$ then we have $$\psi\left(x^{\mu}\right)=-\frac{1}{c} \...
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Harmonic (coherent or not) waves from inflation?

I am just wondering if inflation could produce harmonic (coherent or not) waves and what are they strength (in the limit of frictionless media) or amplitude now for each mode, and if we are searching ...
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Superposition v/s Superimposition

What is the difference between 'superposition of waves' and 'superimposition of waves'?
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-2 votes
1 answer
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Why is the wave impedance calculated as $\eta = \eta_0 / \sqrt{\epsilon_r} = \dfrac{377}{\sqrt{4.0}} = 188.5 \ \Omega$?

I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following: Plane Waves in a Lossless ...
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6 votes
3 answers
200 views

Why don't plane waves always expand according to Huygens' principle?

I have seen a few videos about Huygens' principle and I don't understand why a plane wavefront doesn't expand both vertically and horisontally. According to my understanding of Huygens' principle, ...
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2 answers
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Why are these tsunami waves so short?

https://youtu.be/wAFYVpX45xs This apparently shows a coast guard vessel riding the Japan tsunami. But while we are told that tsunami waves haves periods of several minutes, these waves seem to take ...
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6 votes
4 answers
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What frequency of cord shaking maintains the same vertical motion for a point on the cord after increasing the wave speed on the cord?

I'm studying for my upcoming AP Physics 1 exam but can't figure out this problem A student shakes a horizontally-stretched cord, creating waves. The graph above shows the vertical position $y$ as a ...
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3 votes
1 answer
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What is the displacement amplitude of a 140 db sound wave?

I am teaching a unit on sound in my upper elementary science class, and my students are curious about how far air molecules are actually being displaced in a sound wave. I told them that if the air ...
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1 answer
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From discrete to continuous superposition of waves, what happens to omega?

The Wikipedia page on group velocity uses the superposition of two cosines (of slightly different wavenumbers and angular frequencies) to show that group velocity $v_g = \frac{d\omega}{dk}.$ The sum ...
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Intensity of Two Slits of Finite Width Pattern

I am a college sophomore in an introductory E&M course. Young & Freedman presents the resulting diffraction/interference pattern when shining monochromatic light through two slits of finite ...
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0 answers
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Intensity of bright bands in interference

Ihad one doubt regarding the intensity of bright bands of interference. i have read somewhere , "all bright interference have same intensity but all bands do not receive same light" can ...
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1 answer
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Frequency and length

Why is pitch inversely proportional to length of an instrument? I think i know meaning of frequency but if anyone can also explain frequency according to higher level physics it shall be great.
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-2 votes
3 answers
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What waves look like?

In high school we have always been taught that wave looks figure $A$ and from there we have learnt amplitude,frequency etc of waves. But in a lot of books, waves are represented by the second figure ...
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2 answers
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Using "Maxwell's curl equations" to get $H_y = \dfrac{j}{\omega \mu} \dfrac{\partial{E_x}}{\partial{z}} = \dfrac{1}{\eta}(E^+ e^{-jkz} - E^- e^{jkz})$

I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following: The Helmholtz Equation In ...
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1 vote
1 answer
60 views

How does $-k^2\left( E^+ e^{-jkz} + E^- e^{jkz} - E_x \right) = 0$?

I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following: Plane Waves in a Lossless ...
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0 votes
0 answers
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Why central bright spot (in youngs double slit experiment ) is not considered as the first bright spot , although the central is brightest one?

I have read that in youngs double slit experiment , the bright spot appears whenever there is a constructive interference (nlambda*D/d) . But i want to know why the first bright spot is taken at n=1 ? ...
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3 answers
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Why can we hear instruments but not voices?

I've seen this graph: But I don't get something. Consider the 2kHz line (highlighted in red). This graph implies we can hear an orchestral instrument at 2kHz before we can hear a human at the same ...
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1 answer
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Reduction of the Helmholtz equation for an electric field with only an $\hat{x}$ component and uniform (no variation) in the $x$ and $y$ directions

I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following: The Helmholtz Equation In ...
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0 votes
0 answers
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Why are the electromagnetic wave equation is represented in a complex number? [duplicate]

The wave function $$ f(x,t) = A \sin (\vec{k}\cdot\vec{x} - \omega t+ \phi) $$ Can graphically describe the linear 2d wave propagation. Why this equations is written in this form: $$ f(x,t) = A [\cos ...
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Does air column change its frequency to one of its modes as and when needed?

The question might make it sound like I'm considering air column to be a conscious entity kinda thing, but what I really mean is, Say I've a tuning fork ringing and I bring it near a test tube with ...
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