Mean Free Path
The average distance traveled by a moving gas particle between successive collisions with other particles.
Governing formula
λ = 1 / (√2 π d² n_V)
SI unit
m
In depth
Inversely proportional to molecular cross-section ($Ï€ d^2$) and particle number density ($n_V$). Increases as gas pressure drops.
Examples in the real world
In high-vacuum chamber systems ($10^{-6} Torr$), mean free path expands to hundreds of meters, reducing molecular collisions.