Question

Which graph in the following diagram correctly represents the potential energy of a pair of nucleons as a function of their separation?

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is D

• Repels strongly at small separations (r < 0.5 fm) → high positive U.
• Attracts at intermediate distances (0.5 fm < r < 2 fm) → negative U.
• Drops to zero for r > 2 fm.

Why D? Only option D uses correct units (U in MeV, r in fm) and matches this behavior.

Others fail because:

• B, C: Wrong units (r in meters, U in keV).
• A: Undefined graph shape (if drawn correctly, could also be valid).

The correct answer is (D) : .