Previous Year NEET Question- Kinetic Theory L-4

Question: The mean free path of molecules of a gas, (radius $r$ ) is inversely proportional to [CBSE AIPMT 2014]#

A) $r^3$

B) $r^2$

C) $r$

D) $\sqrt{r}$

Answer: $\sqrt{r}$#

Solution:#

Mean free path (I) is given by $$ l=\frac{1}{\sqrt{2} n \pi d^2} \Rightarrow l \propto \frac{1}{d^2} $$

So, $\quad l \propto \frac{1}{r^2}$