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 :

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(A) is false but (R) is true

(A) is true but (R) is false

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

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

answer is B.

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Detailed Solution

Step 1: Understanding the Statements

Assertion (A): The binding energy per nucleon (BE/A) is the average energy required to remove a nucleon from the nucleus.

It is observed that for nuclei with mass numbers between 30 and 170, the binding energy per nucleon is nearly constant (~8 MeV).

This happens because, in this range, nuclear forces reach saturation, meaning each nucleon interacts with only its closest neighbors.

Assertion (A) is correct.

Reason (R): The nuclear force is a short-range force, acting significantly only within distances of about 1–2 femtometers (fm).

Unlike gravitational and electrostatic forces (which are long-range), nuclear forces do not act over large distances.

Since the reason states that nuclear force is long-range, which is incorrect, Reason (R) is false.

Step 2: Choose the Correct Option

The correct choice is:

(A) is true, but (R) is false.

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