Q 11-12-009NEETNEET 2020Top questionEasy
The mean free path for a gas, with molecular diameter d and number density n can be expressed as :
Answer: (B) $\dfrac{1}{\sqrt{2}\,n\pi d^2}$
A molecule sweeps out a collision cylinder of cross-section $\pi d^2$. Allowing for the motion of the other molecules (the factor $\sqrt{2}$):
$$\lambda = \frac{1}{\sqrt{2}\,n\pi d^2}$$
Solution by Sreeraj P, M.Sc Physics