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mean free path

(average length that a particle travels before interaction)

The term mean free path is used in the physics of moving particles (atoms, electrons, photons, etc.) to indicate the average length they travel between interactions. When performing calculations in a substance where some type of particle moves around, estimates of the consequences can be calculated by assuming all the particles always move the same distance between interactions, using the mean free path as that distance. The mean free path can be determined from the number density and the cross section of interactions, as might be calculated from the minimum intervening distance between the particles' centers at which the particles interact. Some situations where it is used:


(physics)
Further reading:
https://en.wikipedia.org/wiki/Mean_free_path
https://en.wiktionary.org/wiki/mean_free_path
http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/menfre.html
https://www.britannica.com/science/mean-free-path
https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/03%3A_Rate_Laws/3.01%3A_Gas_Phase_Kinetics/3.1.03%3A_Mean_Free_Path
http://physics.bu.edu/~redner/211-sp06/class-macro-micro/kinetic_meanfreepath.html

Referenced by pages:
cross section
decoupling
diffusion damping
free streaming
optical depth (τ)
recombination
Rosseland mean opacity

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