Question

The number of air molecules per cm³ increased from 3 × 10¹⁹ to 12 × 10¹⁹. The ratio of collision frequency of air molecules before and after the increase in number respectively is 

(1) 1.25 

(2) 0.25 

(3) 0.75 

(4) 0.50

Answer 1

Correct option is (2) 0.25 

Collision frequency,

∴ f ∝ n_v, n_v is number density