Correct Answer - Option 2 : 10

^{-4} /m

__Concept:__

Mean Free Path (λ):

- The distance travelled by a gas molecule between two successive collisions is known as a free path.
- During two successive collisions, a molecule of gas moves in a straight line with constant velocity.
- The average distance that a particle can travel between two successive collisions with other particles.

\(\lambda = \frac{{Total\;distance\;travelled\;by\;a\;gas\;molecule\;between\;successive\;collisions\;\;}}{{Total\;number\;of\;collisions}}\)

\(\Rightarrow \lambda = \frac{1}{{\sqrt 2 \pi n{d^2}}}\)

Where,

n = number of molecules per unit volume and

d = diameter of a molecule