2020 Phase-2 Kinetic TheoryMean free path of gas molecules Medium Question 15 of 34 in Kinetic Theory

The Mean Free Path $\lambda$ for a gas molecule depends upon diameter d of the molecule as

A $\lambda\propto\dfrac{1}{d}$
B $\lambda\propto\dfrac{1}{d^2}$
C $\lambda\propto d$
D $\lambda\propto d^2$

The answer is B.

Solution

The mean free path is given by $\lambda=\dfrac{1}{\sqrt2\,\pi d^2 n}$, where $n$ is the number density and $d$ is the molecular diameter. Hence $\lambda\propto\dfrac{1}{d^2}$.

Concept Mean free path of gas molecules

Kinetic Theory in past papers

34 questions from this chapter have appeared across 19 exam years.