Mean free path of a gas moleculeगैस अणु का माध्य मुक्त पथ

NCERT Fig 12.7 · interactive diagram

Parts and their functions

• Zig-zag path (टेढ़ा-मेढ़ा पथ) — Straight lines between collisions (red dots); the average length of a straight piece is the mean free path l.
• Collision cylinder (संघट्ट बेलन) — In time Δt the molecule sweeps volume πd²⟨v⟩Δt; it collides with every molecule whose centre is inside.
• Diameter 2d (व्यास 2d) — Two molecules of diameter d touch when their centres are d apart, so the cylinder radius is d.
• l = 1/(√2 n π d²) (l = 1/(√2 n π d²)) — Smaller for a denser gas (larger n) or bigger molecules. For air at STP l ≈ 10⁻⁷ m, hundreds of molecular diameters.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 12.7. Report a mistake