Magnetic properties of diamond: Evaluate the assertion–reason pair—Assertion (A) For diamond, μ_r = 1. Reason (R) Diamond is a diamagnetic material.

Introduction / Context:
Magnetic materials are characterized by susceptibility χ and relative permeability μ_r = 1 + χ. Diamagnetic materials have small negative χ, leading to μ_r slightly less than 1. Diamond, an sp^3-bonded carbon crystal, is strongly covalent and exhibits diamagnetism with very small magnitude.

Given Data / Assumptions:

• Assertion claims μ_r equals exactly 1 for diamond.
• Reason states that diamond is diamagnetic.

Concept / Approach:

Because diamond is diamagnetic (χ < 0 but |χ| ≪ 1), its μ_r is close to but not exactly 1 (μ_r = 1 + χ < 1). Thus the assertion is strictly false, while the reason is true. The reason does not support the assertion; if anything, it contradicts it by implying μ_r is slightly less than 1.

Step-by-Step Solution:

Verification / Alternative check:

Measured susceptibilities of many diamagnetic insulators are on the order of 10^-6 to 10^-5 (negative), confirming μ_r is slightly below 1.

Why Other Options Are Wrong:

• Any option implying A true is inconsistent with the definition μ_r = 1 + χ and χ < 0 for diamagnetics.

Common Pitfalls:

• Rounding μ_r to 1 for convenience; exact statements should distinguish “≈1” from “=1”.

Final Answer:

A is false but R is true