Answer: λ/2.
- A 2λ
- B λ/2
- C 4λ
- D λ
Correct answer: B. λ/2
Explanation: At constant T, doubling pressure doubles the number density n (since PV=nRT, n=P/kT at fixed T). Since λ ∝ 1/n, the mean free path becomes λ/2.
Not all gas molecules move at the same speed - the Maxwell-Boltzmann distribution shows the spread, with the most probable speed vp slightly less than the average vavg, which is slightly less than the root-mean-square speed vrms used in the pressure formula.
Concept context
Kinetic theory of gases connects molecular motion to pressure and temperature, explaining gas laws, specific heats, and molecular speeds.