Polarization mechanisms and temperature: Electronic and ionic polarization in a polyatomic gas are approximately independent of temperature, whereas the orientation polarization depends on temperature. Evaluate the assertion–reason pair.

Introduction / Context:Dielectric polarization in gases and dilute media arises from multiple mechanisms. Electronic and ionic polarizations are associated with displacement of electron clouds or ions relative to nuclei and are effectively instantaneous for alternating fields at ordinary frequencies; they depend very weakly on temperature. Orientation polarization, however, is due to alignment of permanent dipoles against thermal agitation and is strongly temperature dependent.

Given Data / Assumptions:

• Electronic and ionic polarizations (a_e and a_i) are treated as constants over moderate temperature ranges.
• Orientation polarization contributes μ_p^2 / (3 k T), which varies as 1/T.
• The assertion states that electronic and ionic polarizations are independent of temperature; the reason incorrectly says orientation polarization is independent of temperature.

Concept / Approach:

Orientation polarization decreases as temperature increases because thermal agitation disrupts dipole alignment. Hence, a plot of susceptibility versus 1/T yields a straight line. The assertion is correct, but the reason contradicts the well-known 1/T dependence, making it false.

Step-by-Step Solution:

Verification / Alternative check:

Curie-like behavior in polar gases confirms 1/T dependence for orientation polarization.

Why Other Options Are Wrong:

• Options claiming R true are inconsistent with the formula and experiments.

Common Pitfalls:

• Assuming all polarization mechanisms vary with temperature the same way.

Final Answer:

A is true but R is false