Question

The mean free path $\ell$ for a gas molecule depends upon diameter, $d$ of the molecule as :

• A. $\ell \,\propto\frac{1}{d^{2}}$
• B. $\ell \,\propto\,d$
• C. $\ell \,\propto\,d^{2}$
• D. $\ell \,\propto\, \frac{1}{d}$

Answer 1

Answer: (A)

$\lambda=\frac{1}{\sqrt{2}\pi\,d^{2} n} \propto\frac{1}{d^{2}}$
$\lambda$= mean free path
d = effective diameter of molecule
n = number density of molecules