Question 153: Atoms & Nuclei

Question

Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The binding energy per nucleon is found to be practically independent of the atomic number A , for nuclei with mass numbers between 30 and 170 .
Reason (R) : Nuclear force is long range.
In the light of the above statements, choose the correct answer from the options given below :

Accepted Answer

Let's analyze both statements:
Assertion (A): Ã¢ÂÂThe binding energy per nucleon is found to be practically independent of the atomic number A, for nuclei with mass numbers between 30 and 170.Ã¢ÂÂ
In fact, for nuclei in this mass range, the binding energy per nucleon is nearly constant (around 7Ã¢ÂÂ8 MeV per nucleon). This is because the attractive nuclear force saturates, leading to a relatively uniform binding energy per nucleon in medium to heavy nuclei.
Therefore, Assertion (A) is true.
Reason (R): Ã¢ÂÂNuclear force is long range.Ã¢ÂÂ
The nuclear force (or strong force) that holds the nucleons (protons and neutrons) together is actually very short-ranged. Its effective range is approximately 1 to 3 femtometers (fm), after which the force rapidly decreases.
Hence, Reason (R) is false.
Since the assertion is correct and the reason is incorrect, the correct answer is:
Option A: (A) is true but (R) is false.

Answer

(A) is true but (R) is false

Answer

Both (A) and (R) are true and (R) is the correct explanation of (A)

Answer

(A) is false but (R) is true

Answer

Both (A) and (R) are true but (R) is NOT the correct explanation of (A)

Atoms & Nuclei

Choose the correct answer: