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# Questions tagged [dispersion]

Dispersion refers to the frequency dependence of the properties of a wave.

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### Speed of light in different mediums with different frequencies

As I know the speed of the light doesn't change while it travels through a vacuum. But while it travels through a prism, it shows different deviation angles to different frequencies. So ...
1k views

### Light in fibre optic cables

Imagine a fibre optic cable stretching from London to New York (5571 km) carrying a data signal This data signal is split into two parts, red and blue light Both signals start travelling down the ...
38 views

### How do you pick the wavenumber at which the group velocitiy is evaluated?

The equation for group velocity is $v_g(k) = \frac{d\omega}{dk}.$ This is obviously a function of $k$ but typically the word is used as if there is a single group velocity and not a whole function. ...
9 views

### Index of refraction of a specific wavelength using Abbe number

I am stuck with a problem, maybe my understand of it is not correct. I would like to solve, given an Abbe number and some index of refraction at a known wavelength, the ior of any wavelength λ. From ...
27 views

### Dispersion relation of a medium

In a dispersive medium I have a wave equation: $$\frac{\partial^2E}{\partial z^2} + \eta \frac{\partial^4E}{\partial z^4} - \frac{1}{c^2}\frac{\partial^2E}{\partial t^2}=0.$$ How can I find the ...
310 views

### The effect of frequency and amplitude on the speed of sound

I don't do physics, but a sound-related question came up in a project. I've googled extensively but I still can't get a hang of the basics. The following are two related questions. Assume the source ...
41 views

147 views

### Dispersion through Glass Slab

My questions related Dispersion through Glass Slab: Why does a parallel surface makes a difference? Why is that light do get disperse in a prism and a glass slab at surface one but at backs normal ...
913 views

### What is the significance of dispersion relation i.e. frequency vs. wave vector relation?

There are lots of pages in my textbook dedicated to this sole relation and frequency vs. wave vector graph. I do not understand what are practical significance and uses of the relation and the graph. ...
17 views

### Dispersion: any software to work out the dispersed waveforms of EMW signals that propagate via interstellar medium for some distance?

I asked this question in the Astronomy site, but seems few people feel interested in, so I hope to have a try here in the Physics site...... Is there any software (toolbox, code, package, paid or ...
121 views

### Sound frequencies travel at the same speed?

as the diagram shows sound frequencies travel at the same speed or each frequency has a given speed ?
274 views

### Time delay of a laser pulse due to 2nd, 3rd and 4th order dispersions

I'll explain my problem : Given a Gaussian pulse with central wavelength 550 nm and a HMFW of 300 nm, and let's assume the pulse is transform-limited. I need to get the pulse through 1mm of quartz. ...
55 views

### Why is group velocity the important velocity?

It seems that universally in all systems, group velocity is the relevant velocity but why? I read that this is the speed of information transmission but why is that the case? How do you define where ...
6k views

### Why do wave packets spread out over time?

Why do wave functions spread out over time? Where in the math does quantum mechanics state this? As far as I've seen, the waves are not required to spread, and what does this mean if they do?
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### What happens to frequency during dispersion?

I'm a bit confused about what happens to frequency during the dispersion of white light passing through a prism. I understand that when a light wave is travelling in one medium, velocity is constant ...
37 views

### Dispersion under Classical and Quantum regimes

If I understand correctly the literature on dispersion, the atom is modeled as an electron bound to an atom by a spring with the electron behaving as a driven, damped oscillator. The electron ...