Question

The mean free path for a gas, with molecular diameter $d$ and number density $n$ can be expressed as :

• A. $\frac {1}{\sqrt{2} n \pi d}$
• B. $\frac {1}{\sqrt{2} n \pi d^2}$
• C. $\frac {1}{\sqrt{2} n^2 \pi d^2}$
• D. $\frac {1}{\sqrt{2} n^2 \pi^2 d^2}$

Answer 1

Answer: (B)

$\frac {1}{\sqrt{2} n \pi d^2}$

Answer 2

Mean free path for a gas sample $\lambda_{m}=\frac{1}{\sqrt{2}\pi d^{2} n}$
where d is diameter of a gas molecule and n is molecular density