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