Mean Free Path

λ = \frac{k _{B} T}{2 π d ^{2} P}

Average distance a molecule travels between collisions.

Variables

λ

Mean free path

Avg distance between collisions

m

k_B

Boltzmann constant

1.38×10⁻²³

J/K

T

Temperature

Absolute temperature

K

d

Molecular diameter

Effective diameter

m

P

Pressure

Gas pressure

Pa

Derivation

λ = 1/(√2 π d² n) where n = P/(kT).

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