# 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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### Applying Doppler's effect when both source and observer are same [closed]

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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### What happens if I send light from two light sources through a single slit?

I have two identical point light sources A & B emitting the same frequency. They are equidistant from the single slit and from the line passing perpendicularly through the middle of the slit ...
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### What is the relevant phenomenon behind Undulatus/Radiatus cloud formations?

I am seeing many people claiming that cumulus clouds that sometimes form periodic wavy patterns (see images for "altocumulus undulatus" or "Radiatus" for instance) have no ...
55 views

### Why temporal and spatial term is multiplied to get the wave equation?

When deriving the wave equation we have: $$y_{spatial} = A\exp(ikx)$$ $$y_{temporal} = A\exp(-i\omega t).$$ Then the overall wave equation is obtained by multiplying both time and spatial component. ...
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### Types of Mechanical Waves

When knocking on a door, does that create a transverse wave or a longitudinal wave? I know it's one of these mechanical waves, but which one?
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### - The minimum distance at which a radar can detect a target is 270 m. Determine the wavelength at which the radar operates if it emits pulses, [closed]

The minimum distance at which the radar can detect a target is 270 m. Determine the length of the waves at which the radar operates if it emits pulses, each of which contains 6,000 electromagnetic ...
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### Is sound essentially motion?

From my understanding, the only way for humans to create sound is by moving our bodies, vocal cords, or by moving other objects. So depending on how fast we or other objects can move, different ...
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### If frequency is the characteristic of a source and remains constant why does it increase when tension of a string is increased?

So as I've been taught,Frequency is a characteristic of the source and it does not change. But,then there are questions where when the tension of a string increased and frequency increases. Can anyone ...
3k views

### Physical interpretation of source term in wave equations

Let me start with an example. If we base our calculations on the Newton's second law without any further mathematical treatment, then our equation describes equilibrium of forces, i.e. it is of the ...
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### Confusion regarding structure of standing waves in organ pipes in non standard cases [closed]

In a resonance tube, resonating frequencies occur at l1 and l2 (suppose). Then how will the standing wave look like when l1<l<l2? And when does a standing wave with different loop length get ...
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### How do I find the reflection coefficient related to the lumped impedances? [closed]

I am having a hard time dealing with lumped impedance in problems related to traveling waves. How can I handle problems where both characteristic impedance and lumped impedance are present, as in the ...
1 vote
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### Does the field vector rotate clockwise for right circular polarization when viewed from behind the source of the wave?

Descriptions and images of right or left circular polarization do differ based on a viewpoint being either behind or in front of the wave source. Furthermore, I see pictorial representations that do ...
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### Why is the total force at a free surface zero?

I am looking into waves on a free surface for which their are two main conditions: Kinematic condition: Particles on the surface remain on the surface. Dynamic condition: Forces acting on the surface ...
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### Crown shape in water waves?

Watching this slow motion video of waves caused by a droplet falling on water, I am puzzled by the first wave shape. The first wave rises with circular symmetry as I expected, but is not even in all ...
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### How is symmetry boundary condition related to reflection of a plane wave from a rigid flat surface?

My question is in in the context of "method of images" when applied to an incoming incident acoustic pr plane wave. For a flat rigid surface in $XY$ system, the surface (positioned at $Y=0$) ...
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### If you are on the moon, would you be able to hear your hands clapping if you're not wearing your spacesuits?

As I understand it, sound needs a medium to travel and more often than not, the medium is the atmosphere, however sound can also travel through solid objects. And even we can hear our own voice ...
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### Could the double slit experiment demonstrate not that particles behave like waves, but that together particles behave as a wave? [closed]

Clearly particles individually pass through slits, be it a single or a double slit experiment. The fact that wave interference is evident in their trajectory may be due to their interaction upon ...
1 vote
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### How can I find if it is gold or lead with waves? [closed]

I would find if a bowl is made of lead or gold know freqencies $w_{1}$ and $w_{2}$ and a vibrator induces waves at $z=0$ (and there are reflected waves). I do it with progressive plane electromagnetic ...
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### What is the amplitude in c) part and why is the phase difference not $\pi$? [closed]

So this is from OCW First part is fairly easy natural frequency comes out to be 10 Hertz,Gamma came out to be 1/2 for two traffic signals and 1 for a single traffic signal, In second part I am ...
1 vote
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I've recently been conducting experiments on the Chladni Plates, testing out how the length of a square Chladni plate (and consequently its area) affects the frequency at which each respective chladni ...
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### Can a standing wave indistinguishable from a travelling wave for a stationary observer?

Say that you place an observer at a point in space where the non-zero amplitude of a standing soundwave is equal to the amplitude of some travelling soundwave (that is, the two opposing travelling ...
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### Is it not possible for true standing waves to appear in nature?

From what I understand, standing waves form when the following conditions are met: 2 waves of equal frequency, amplitude, and polarization are travelling in opposite directions. So if any of those ...
1 vote
324 views

### How can I calculate the number of nodes on a plucked string?

Given the length of the guitar string, can you predict the number of nodes that would exist on that string? My textbook says that there are an infinite number of harmonics that can be created when a ...
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### Difference between structural acoustics and flow induced acoustics

I'm researching about sound induced inside water pipe and came up with some questions. For numerical acoustic calculation, I found two ways. Using acoustic analogy such as Lighthill equation or ...
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### The initial conditions for the harmonic travelling waves

I'm given the following problem: For a harmonic travelling wave travelling in the positive direction, the initial transverse speed is 3 m/s and the initial $y$ displacement or transverse ...
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### Frequency of Sound Waves

Is the frequency of the echo (resulted from the reflected sound wave) equal to the frequency of the original sound wave?
1 vote
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### Two-Ray Ground-Reflection Model: Understanding the Difference in Phase Offsets at the Receiver

Currently, I'm trying to understand the Two-Ray Ground-Reflection Model. During my research, I came across the following simplification expressing the received power as follows (taken from Wikipedia): ...
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### Phase Angle: AC Circuit

I am seeing this everywhere when I look up impedance and reactance for AC circuits. Below is a picture below from the website here. They say the formula for the phase angle is $y=\sin(\omega t+\phi)$....
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### Paraxial Spherical wave emanating from point source

I'm reading through chapter 5.3.1(Impulse response of a Positive lens), in Goodman's "Fourier Optics"(p.109). An object is placed a distance $z_1$ in front of a lens. If we place a point ...
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### What is an electromagnetic wave exactly?

This question might be very silly, but I am really confused about it from several days. Look transverse waves on a string propagate along the string due to the electromagnetic (EM) forces between ...
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### Is the argument of the $\sin$ function for a monochromatic plane wave dimensionless?

I was looking at the following representation of a monochromatic plane wave: $$F(\vec x, t) = A\sin(2\pi\nu(\vec x \cdot \hat n - ct) + \phi)$$ but, upon analyzing the argument of the sin function, ...
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### On sum of amplitudes in Wave Mechanics

Consider Schroedinger equation, which I write in the form $$(\mathscr{L}+V)\psi=0$$where $\mathscr{L}$ is the kinetic and time-derivative operator. Now, imagine I have two point sources 1,2 with ...
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### The Role of Harmonic Frequencies in Natural Phenomena and its Uniqueness [closed]

My question arises from why there is such an intrinsic relationship with harmonics in physics, not only in terms of the mathematics we use to describe the world in a simple way for us, but it also ...
1 vote
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### How do you calculate phase from sin wave equation?

So if a wave equation is $A \sin \left(k x - \omega t + \phi \right)$ then how can you calculate what the phase would be? From the graph, it is visible to see where the graph has shifted but just by ...
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### How do the forces involved in EMR continue to occilate past emmision of a photon

If electric fields are created by an accelerated charged particle, such as an electron, and magnetic fields are generated by electric fields in motion, what are the individual fields that make up ...
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### Why the consecutive spherical wavefronts produced by a rest point source are not equidistant? [closed]

I learnt that a point source produces spherical wavefronts and i know the reasoning behind that too and while studying the concept again a question popped in my mind, that "Are those spherical ...
1 vote
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### Does a linearly accelerating spherically symmetric body emit gravitational waves

According to Birkhoff's Theorem, any spherically symmetric body will not emit gravitational waves. I can understand this for an object that is contracting and expanding because from far away the ...
1 vote
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### Is there a Doppler effect on the surface of an expanding balloon?

Imagine a stationary transmitter which vibrates the surface of the balloon and a stationary receiver half way around the balloon that can pick up these waves. Let the balloon expand. Will the ...
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### How can acoustic velocity of plane wave be derived using acoustic pressure?

I am going though the section on plane travelling waves from the book by G.D.Pierce,"Acoustics: An Introduction to Physical Principles and Applications". I am unfortunately stuck at a place ...
1 vote