Assertion (A): Diamagnetic substances exhibit magnetism.
Reason (R): Diamagnetic materials do not have a permanent magnetic dipole moment.
Reason (R): Diamagnetic materials do not have a permanent magnetic dipole moment.
- (A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- (B)Both Assertion (A) and Reason (R) are true and Reason (R) is NOT the correct explanation of Assertion (A).✓ Correct
- (C)Assertion (A) is true but Reason (R) is false.
- (D)Assertion (A) is false and Reason (R) is also false.
Answer: (B)
Solution
Diamagnetic substances do show magnetism: in an external field they develop a weak induced moment directed opposite to the field, so Assertion (A) is true.
Their atoms have paired electrons and hence no net permanent magnetic moment, so Reason (R) is also true.
However, the induced (and therefore observable) diamagnetism arises from the change of electronic orbital motion in the applied field; the mere absence of a permanent moment does not by itself explain why they exhibit magnetism, so (R) is not the correct explanation of (A).
Their atoms have paired electrons and hence no net permanent magnetic moment, so Reason (R) is also true.
However, the induced (and therefore observable) diamagnetism arises from the change of electronic orbital motion in the applied field; the mere absence of a permanent moment does not by itself explain why they exhibit magnetism, so (R) is not the correct explanation of (A).
CBSE Class 12 Board · 2023 · Single correct option