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7 votes
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Can you have diffraction without a slit, simply by reducing the size of light source?

In case you have in mind a point-source, then - no. By definition of diffraction (you can check it in wiki) it's light bending around obstacles corners or aperture. By definition, point-source of ...
Agnius Vasiliauskas's user avatar
5 votes

Can electromagnetic fields "retain" records?

Flash memory stores information in the form of charges stored (or not stored) in an array of special transistors. The information can equivalently be thought of as being stored in the static electric ...
Puk's user avatar
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5 votes

Where is the compression for this sound wave?

This question is ... unfortunate. Air molecules do not have equilibrium positions, and to imagine that sound waves propagate through gases in this way is a profound misunderstanding. Of course, the ...
J. Murray's user avatar
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4 votes

Can you have diffraction without a slit, simply by reducing the size of light source?

All objects diffract and diffraction is light's interaction with obstacles, specifically with their edges. The reason we see the effect more pronounced with smaller slits/openings is because the ...
hyportnex's user avatar
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3 votes

Is each INDIVIDUAL photon a PHYSICAL wave?

Firstly, we can only say anything about the quantum world in as far as we can make observation of it. For that reason, the underlying mechanisms that cannot be directly observed always rely on how we ...
flippiefanus's user avatar
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3 votes

Can electromagnetic fields "retain" records?

Without any device electromagnetic waves move through space at the speed of light. So they can store information, but the information is moving in space at the speed of light. Using an optical cavity ...
Jagerber48's user avatar
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2 votes
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Why carrier wave cannot transfer information?

there is some bandwidth to the frequency of the carrier wave which imply that we can identify some changes. That bandwidth is very thin and carries noise. Modulating the carrier wave with any useful ...
Ján Lalinský's user avatar
2 votes
Accepted

How do the amplitudes of longitudinal wave harmonics in a string vary with excitation (pluck) position?

Short Answer The harmonic amplitudes of the longitudinal "pluck" would follow the same pattern as the transverse pluck. Longer Answer Without having to rederive the harmonic amplitudes for ...
Michael M's user avatar
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2 votes

How to standardize the energy of a Dirac delta function relative to sample rate (width) and amplitude?

For a sampled signal, a one sample pulse has a white DTFT (discrete time Fourier transform) spectrum. A wider pulse has a high frequency cutoff. The energy in the pulse is proportional to its duration,...
John Doty's user avatar
  • 20.1k
2 votes

Graphical interpretation of complex electric fields

This is a notation we use because it makes it much much easier to work with the fields. We just remember that we have to take a real part of the complex quantities to get a real field value. So the ...
BaddDadd's user avatar
2 votes
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Multiple same maximum amplitudes of a pendulum

You are correct. If the pendulum was an ideal object with no friction, it would always swing back to the maximum amplitude (point C). In reality the pendulum will lose energy due to friction with air, ...
Alessandro Bertoli's user avatar
2 votes

Poynting vector of a scalar wave

I'll start with the 1 dimensional case and generalize to n dimensions afterwards. For an idealized string the wave equation is, $$\rho \frac{\partial^2 \psi}{\partial t^2} = T \frac{\partial^2 \psi}{\...
George Chiporikov's user avatar
1 vote

Where is the compression for this sound wave?

Think of the dots in you diagram as the centre of mass of a small volume element containing a number of molecules (but to necessarily the same molecules) defined when there is no sound wave. As a ...
Farcher's user avatar
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1 vote

Why does the sine wave graph gets inverted when we put $t=0$ in $A\sin(wt-kx)$ and what does it signify?

Suppose you have a $1$D transverse sin wave traveling down a string. How would you mathematically describe it? You must find a function $y = f(x,t)$ that gives the height $y$ for each point $x$ and ...
mmesser314's user avatar
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1 vote

Why does the sine wave graph gets inverted when we put $t=0$ in $A\sin(wt-kx)$ and what does it signify?

In theory, there is no physical meaning, since the answer is coordinate dependent (when is $t=0$?), and (write this down): Physics does not depend on your coordinate system. But maybe, in this case (...
JEB's user avatar
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1 vote
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Wave dispersion relation as a differntial equation

Here is my way of proceeding. Most of it agrees with you, but I can't quite pin down where we differ. Perhaps the mixed-partial trick of interchanging the $i$ and $j$? The essential feature of a wave ...
mike stone's user avatar
  • 52.4k
1 vote

Wave dispersion relation as a differntial equation

Write this in coordinates. Let $$\left[\nabla \mathbf k\right]_{ij} = \frac{\partial k_j}{\partial x_i}$$ then $$\left[\mathbf v \cdot \nabla \mathbf k\right]_j = \sum_i v_i \frac{\partial k_j}{\...
hyportnex's user avatar
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1 vote
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How many 'wavelengths of length' can a wave have?

The mathematical wave you are showing , has no limit of length it can go from minus infinity to plus infinity, When a mathematical wave function is used to fit specific physical behavior, as waves ...
anna v's user avatar
  • 233k
1 vote
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Frequency of light wave doesn't change with media

Let's simplify to one dimension with a $+x$ propagating wave, boundary at $x=0$. The left wave is: $$\psi_L(0, t) = A_L e^{i(kx-\omega_L t)}=A_L\exp(-i\omega_L t) $$ On the right: $$\psi_R(0, t) = A_R\...
JEB's user avatar
  • 32.7k
1 vote

Possibility of complex EM waves

Remember, the electric field strength $\vec{E}$ is defined by the force $\vec{F}$ experienced by a charge $q$: $$\vec{F}(\vec{r},t)=q\vec{E}(\vec{r},t)$$ Both charge $q$ and force $\vec{F}$ are real ...
Thomas Fritsch's user avatar
1 vote

Possibility of complex EM waves

Mathematically, you can consider complex valued solutions of Maxwell's equations. Physically, it doesn't make sense to consider a complex electric field. Consider the equation for the Lorentz force $$ ...
Andrew's user avatar
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1 vote

Can you have diffraction without a slit, simply by reducing the size of light source?

Let us consider some practical example. There exist microscopic lasers (https://doi.org/10.1364/OPTICA.476758), they have mirrors, so there is diffraction on a mirror.
akhmeteli's user avatar
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1 vote
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How do you express the electric and magnetic field of a TEM uniform plane wave due to a magnetic current density?

If you're talking about the fields generated by a current of magnetic charges, the electric-magnetic duality relation is of use. It says that any solution of Maxwell's equations in vacuum may be ...
Michael Seifert's user avatar
1 vote

How wave speed affects perception?

They would be waves traveling through different media with their frequencies set so that they have the same wavelength. So you would see them as different colors or hear them as different pitches.
Dale's user avatar
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1 vote

What really is oscillatory motion in physics?

Oscillatory motion, in physics, refers to a repetitive, back-and-forth movement around a central point or equilibrium position. This type of motion is characterized by a regular pattern of variation ...
Brendan Darrer's user avatar
1 vote

Why carrier wave cannot transfer information?

A truly carrier wave is a single frequency and fixed amplitude. Therefore the only information you can extract from it is its frequency, amplitude, and maybe phase. In communications we convey data by ...
Jagerber48's user avatar
  • 13.6k
1 vote

Is it possible to, like white noise, excite all audio frequencies equally, but with a more immediate & less random burst? Like a signal discontinuity?

A step has a $f^{-2}$ power spectrum, not white. A delta function (impulse) has a white noise spectrum. You may approximate it with a narrow pulse. A pseudorandom binary sequence or pseudonoise ...
John Doty's user avatar
  • 20.1k
1 vote

Proving a given vector to be a four-vector

We know, the four-position $$x^\mu=(ct,\vec{r})$$ is a four-vector. We also know, for a plane wave its phase at any certain point in spacetime $$\phi=-\omega t+\vec{k}\cdot\vec{r},$$ must be a four-...
Thomas Fritsch's user avatar

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