Question

Two statements are given, one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C) and (D) as given below.
% Assertion Assertion (A): During the formation of a nucleus, the mass defect produced is the source of the binding energy of the nucleus.
Reason (R): For all nuclei, the value of binding energy per nucleon increases with mass number.

• 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, but Reason (R) is not the correct explanation of Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Both Assertion (A) and Reason (R) are false.

Hint:

The binding energy per nucleon increases with mass number for light nuclei, but it reaches a peak for medium-sized nuclei like iron. For heavier nuclei, the binding energy per nucleon decreases.

Answer 1

The Correct Option is C

- Assertion (A): The mass defect in nuclear formation directly corresponds to the binding energy. Mass defect is the difference between the nucleus's mass and the combined mass of its individual nucleons. This deficit mass is transformed into binding energy, as per Einstein's equation \( E = \Delta m c^2 \). Consequently, Assertion (A) is accurate.
- Reason (R): The binding energy per nucleon does not exhibit continuous increase with mass number across all nuclei. For lighter nuclei, it rises with mass number, but it peaks for mid-sized nuclei (approximately iron-56) and subsequently declines for heavier nuclei. Therefore, Reason (R) is inaccurate, as the binding energy per nucleon does not universally increase for all nuclei.Thus, the accurate response is option (C): Assertion (A) is true, while Reason (R) is false.