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NEET PHYSICSKinetic TheoryEasy

Question

The mean free path for a gas, with molecular diameter dd and number density nn, can be expressed as:

A

12nπd2\frac{1}{\sqrt{2}n\pi d^2}

B

12n2πd2\frac{1}{\sqrt{2}n^2\pi d^2}

C

12n2π2d2\frac{1}{\sqrt{2}n^2\pi^2 d^2}

D

12nπd\frac{1}{\sqrt{2}n\pi d}

Step-by-Step Solution

  1. Definition: The mean free path (λ\lambda) is the average distance a gas molecule travels between successive collisions.
  2. Derivation Concept: Consider a molecule of diameter dd moving with average speed vv. It sweeps out a cylinder of volume πd2vΔt\pi d^2 v \Delta t in time Δt\Delta t. The number of collisions is determined by the number density nn. To account for the motion of all other molecules, a relative velocity factor of 2\sqrt{2} is introduced.
  3. Formula: The standard expression derived in the Kinetic Theory of Gases is λ=12nπd2\lambda = \frac{1}{\sqrt{2}n\pi d^2}.
  4. Analysis of Options: Option A matches the standard formula. The other options have incorrect powers of nn or dd.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Kinetic Theory. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSKinetic Theorymoleculardiameternumberdensityexpressed

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