According to the kinetic theory, the molecules of a gas move in different directions and collide with each other.
The mean free path is the average distance travelled by a moving particle (such as an atom, a molecule, a photon) between successive collisions, that modify its direction.
Let the distances covered by molecules of gas in N collisions be λ1, λ2, λ3,…..λN. Then, the mean free path can be defined as
If t is the time taken to cover the path and υ is the mean speed of molecule, then
