Question 421:
moderateThe mean free path $l$ for a gas molecule depends upon diameter, $d$ of the molecule as (2020-Covid)
The expression for mean free path is $l = \frac{1}{\sqrt{2}\pi n d^2}$. From this formula, it is clear that the mean free path is inversely proportional to the square of the diameter, $l \propto \frac{1}{d^2}$.
Question 422:
moderateThe mean free path of molecules of a gas, (radius $r$) is inversely proportional to: (2014)
The mean free path is given by $\lambda = \frac{1}{\sqrt{2}\pi n d^2}$. Since molecular diameter $d = 2r$, we have $\lambda \propto \frac{1}{d^2} \propto \frac{1}{r^2}$. Therefore, it is inversely proportional to $r^2$.