Questions tagged [mean-free-path]
The average length that a molecule will travel in a fluid before colliding with another molecule.
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Rigorous derivation of the mean free path in a gas
Can anyone supply me with a derivation of the mean free path, of
particles in a Maxwell Boltzmann Gas?
Cited in various literature is the formula,
\begin{align}
\begin{split}
\ell&=\frac{1}{\...
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Do photons slow down this much in the Sun's gravitational field?
I just heard someone mention that photons take 40 thousand years to travel from the centre of the Sun to its
surface which is roughly 700,000 kilometres. How is that possible if the speed of light/...
user280085
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Does it make sense to define the mean free path in quantum mechanics?
The mean free path defined in classical molecule dynamics has a strong classical flavor. Is it sensible to generalize the idea to quantum mechanics?
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Why is the mean free path length of an electron in a solid described by a "universal curve"? (doesn't include electron density)
I've been experimenting with XPS (X-ray photoelectron spectroscopy) and learned that the depth from which the observed electrons originated depends on their mean free path length, which makes sense to ...
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RMS Free Path vs Mean Free Path
I am trying to determine the mathematical difference between mean free path and root-mean-square free path. For an ideal gas, the relaxation time is $$\tau=\frac{1}{\sqrt2 \pi nd^2 \bar v}$$ and the ...
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What does ultra-rarefied gas mean?
Without using any math, can you explain to me what a rarefied gas is? And then what an ultra-rarefied gas is? I'd like to understand it from a conceptual level if you can make connections to other ...
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Number of fog droplets in the air
I have an issue with the official solution to this problem from BelPhO:
Visibility on the road is 100 m. Assuming that the diameter of a fog
droplet is 1 micron, estimate the concentration of fog ...
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Usually, how much does a phonon travel without scattering?
Phonons propagate without problems in a lattice, until they scatter on something, like a defect, an electron, or another phonon. But in a typical solid at room temperature, how much (or how long) is ...
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Derivation of relativistic mean free path
I am working through a short derivation found in Abramowicz 1991 regarding the mean free path of a photon.
We have a fluid moving in a particular direction with velocity $v$ and in an inertial rest ...
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Which average are we taking in a rigorous calculation of the mean free path in a gas?
This is a question at one level beyond the standard introductions to kinetic theory. I want to know which average we are taking when we talk about a mean free path in a gas. I recently read
Steve T. ...
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Formula for mean free path in two dimensions
I'm running some simulations of particle collisions in two dimensions with discretised time and space. In essence, particles only collide if they occupy the same location (cell) at the same time step. ...
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Mean free path of UV photon
I was wondering if there's a simple way to compute the mean free path of UV photons in a optically thick medium with density n.
I've looked up at the literature ...
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Ion charge exchange mean free path
I am using the following equation to calculate the mean free path between a deuteron ion and background gas:
$$\lambda_{d-gas} = \frac{kT_{gas}}{p_{gas} \, \sigma_{10}}$$
Where $\sigma_{10}$ is the ...
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Mean free path regarding billiards
Is there a generalization of the mean free path for macro-objects such as the distance the white billiard ball could travel before hitting an other billiard ball?
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How to (hypothetically) calculate $\tau$, the mean free time?
Referring to the Drude Model, I've seen a lot of excellent questions on whether $\tau$ should be thought of as the "average time between collisions" or the "average time until the next collision", and ...
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